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Public International Law/Sources of International Law

Author: Craig Eggett

Required knowledge:

Learning objectives: to understand the nature of sources in international law; to understand the relationship between the sources. = Introduction =

The topic of the ‘sources’ of international law is essentially concerned with one central, and rather basic, question: how are international rules made? Despite, or perhaps because of, the foundational nature of this question, there are few areas of international legal scholarship that have generated such long-running and vociferous debate. Questions about the sources of international law have always been central to international legal discourse and understanding the language of the sources remains critical for all actors wishing to engage with the international legal system. The chapters that follow explore the different ways in which international legal rules are created and, in doing so, they reflect on the theory and practice of the sources of international law. This chapter introduces some broader questions about the sources of international law, with the aim of setting the scene for the examination of the individual sources that follows. To this end, this chapter proceeds in four main parts. First, it considers in greater detail the concept of a ‘source’ in international law. Second, it examines the content of article 38 ICJ Statute. Third, it considers the reality of the operation of the sources in practice. Fourth, it explores questions of hierarchy in the sources and norms of the international legal system.

= The Concept of a ‘Source’ of International Law =

As a preliminary point, it is useful to consider the precise meaning of ‘source’, as some authors have used the term to describe a range of foundational aspects and processes of the international legal system. Some scholars have understood this term to cover the origins and rationale of international law as such. The use of the term ‘source’ to include the background and objectives of a rules-based international order is broader and rather unconventional. More commonly, when international lawyers consider the sources of international law, they are concerned with the processes through which international legal rules are created. The focus is on the procedures and practices that lead to the formation of international law, thereby allowing them to identify the binding law that regulates the behaviour of actors in the international legal system.

Sources and the International Legal System
The international legal system, like all legal systems, is composed of primary and secondary rules. Primary rules are those that create obligations, grant rights, or change a legal situation. Examples include the prohibition of the use of force, rules on human rights, and provisions that set conditions for membership to international organisations. Conversely, secondary rules are those that regulate the creation, modification, and application of other rules. Examples include rules on the interpretation of treaties and the law of state responsibility. The rules on the sources of international law are a category of secondary rules; they set out the criteria for the creation of other international rules. The presence and operation of secondary rules is indispensable for the existence and functioning of the international legal system. As such, when searching for answers to questions about the sources, it is necessary to confront difficult questions about the foundations of international law as a normative order. In turn, the theory and practice of the sources plays a role in shaping international law as a legal system. In other words, there is a co-constitutive and mutually influential relationship between the sources of international law and the international legal system. As will be demonstrated in the sections that follow, sources questions touch on issues such as the functions of different international actors, including the continued dominance of states as participants in the legal system, and the relationship between international legal norms.

Categories of Sources?
There is a tendency to attempt to delineate between different categories of sources of international law. Most commonly, authors have distinguished between formal and material sources of law. Formal sources are the methods or process of law-making that result in binding legal rules. The formal sources of international law provide criteria against which the validity of a prospective rule is to be judged. If these criteria are fulfilled, there is a valid and legally binding rule of the system. If not, not such rule is to be found. Examples include the procedures for the formation of a treaty as reflected in the VCLT 1969. Conversely, material sources do not in and of themselves create binding legal rules, but may provide evidence for the existence of such rules and their content. Material sources include a broad range of instruments that shed light on whether the criteria set out in the formal sources have been fulfilled. Examples include some resolutions of international organisations, the output of the ILC and judicial decisions.

Other categories that have been suggested include a division between primary and secondary (or subsidiary) sources. These terms may be used to describe the same distinction – between criteria for the creation of binding rules and the evidence for the fulfilment of such criteria – reflected in the formal/material dichotomy. It should be noted with caution that the use of the terms ‘primary’ and ‘secondary’ in this way is distinct from the description of primary and secondary rules referred to above. It is also important to note that this use of primary and secondary should not be taken to imply a formal and strict hierarchy between the sources as may be implied from such use in other legal systems. The question of hierarchy between sources and norms is dealt considered below.

= Article 38 ICJ Statute =

Article 38 of the ICJ Statute is the traditional, and perhaps inevitable, starting point for an examination of the sources of international law. As such, it is worth reproducing the text of this provision in full:

 * 1) The Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply:

  international conventions, whether general or particular, establishing rules expressly recognized by the contesting states;   international custom, as evidence of a general practice accepted as law;   the general principles of law recognized by civilized nations;   subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations, as subsidiary means for the determination of rules of law.

  This provision shall not prejudice the power of the Court to decide a case ex aequo et bono, if the parties agree thereto.

As evidenced by the opening sentence, this provision is, strictly speaking, merely the lex arbitri (Latin: ‘applicable law’) provision of the ICJ. That being said, article 38 has traditionally been viewed as an authoritative statement of the sources of international law. The continued accuracy of this position can be challenged and is considered both in this chapter and the ones that follow, yet it is evident that any discussion of the sources should include an examination of article 38 ICJ Statute. This provision is, at a basic level, composed of three main parts. First, article 38(1)(a)-(c) sets out the (formal or primary) sources of international law: treaties, customary international law, and general principles of law. Second, article 38(1)(d) sets out the ‘subsidiary means’ for the determination of international rules. Third, article 38(2) allows for the Court to resolve a dispute before it on the basis of (a form of) equity, should the parties agree.

The specificities of each of these sources is considered elsewhere, so it suffices to make a handful of general observations here. On the traditional understanding of international law, it is states who play the exclusive, or at least dominant, role in the formation of international rules and an initial reading of article 38 seems to confirm this. Indeed, the mainstream view has traditionally been that states are not bound by international rules unless they have consented to them. While it is clear that states remain prominent actors in international law-making, it can be now be legitimately questioned whether the creation of rules remains the sole prerogative of states. This question is taken up below and features in the chapters on the individual sources.

Article 38(1)(d)’s reference to ‘subsidiary means’ reflects the aforementioned distinction between formal and material sources. That is, the means referred to in this provision – judicial decisions and the teachings of the most highly qualified publicists – are sources of evidence for the determination of rules of law on the basis of the formal sources listed in article 38(1)(a)-(c). These means are not sources of binding rules in and of themselves, but can provide evidence that the conditions set out in (one of the) formal sources have been fulfilled. This is confirmed by the reference to Article 59 ICJ statute, which states that the decisions of the Court have ‘no binding force except between the parties and in respect of that particular case”’ As will be explained below, that judicial decisions are not binding as such does not mean that the jurisprudence of international courts and tribunals does not play an important role in shaping the international legal system.

The reference to ex aequo et bono (Latin: ‘according to the right and the good’) in article 38(2) identifies the possibility that a dispute before the Court may be settled on the basis of equitable considerations, should the parties agree. This is a reference to a specific form of equity free from interaction with legal norms. To date, this provision has never been invoked before the ICJ.

= The Reality of International Law-Making =

There is extensive scope for rich theoretical discussion on the sources of international law. As with all areas of the discipline, such discussion is critical if the international legal system is to be able to achieve its objectives. Regardless of the position taken on the exhaustiveness of the article 38 or the role of state consent, this provision alone cannot paint an accurate picture of the practice of international law-making. International law is a decentralised legal system comprised of a plurality of actors and legal regimes. As a result, the sources of international law function in a dynamic manner, relying on a complex web of interactions between different bodies – such as states, international organisations, and judicial bodies – and reliance on a range of instruments, such as treaties, various decisions, and other ‘soft law’ instruments. This is only partly captured by the reference to judicial decisions and teachin of publicists in article 38(1)(d) ICJ Statute.

Example: The ILC and the Development of International Law

The work of the ILC has been instrumental in many areas of international law. The Commissions work has serves as the basis for treaties, including the VCLT, and its conclusions are frequently cited with authority. For example, the product of the ILC’s work on state responsibility (ARSIWA) – itself a comprehensive review of state practice, judicial decisions, and an array of other instruments, was confirmed to be part of customary international law but the ICJ in the Bosnian Genocide case.

= Hierarchy in the Sources of International Law =

At first sight, it may appear that the sources listed in article 38(1)(a)-(c) ICJ Statute are listed in a specific order, denoting a hierarchy between them. This is not the case. There is no hierarchy between the sources of international law. There can be multiple rules that have similar or identical content, but emanate from different sources of international law. For example, in the Nicaragua case, the Court confirmed the parallel existence of customary and treaty rules regarding the use of force. This question of a hierarchy between the sources is separate from that of hierarchical relationships between international norms. While there are clear examples of normative hierarchies, a rule will not prevail over another because of its source. The question of a hierarchy between the sources is also separate from the question of the role and importance of the different sources of international law more generally. For example, much of international law-making is done by states through concluding treaties. There are now thousands of bilateral and multilateral treaties covering a broad range of topics. As such, much of international law will be treaty law. Conversely, it may be possible to argue that many of the fundamental rules of general application are custom or general principles. Once again, these realities do not denote a hierarchy between the sources, but different roles played by the rules emanating from the different sources in different areas of international law. Broadly speaking, there are three aspects of international law that are referred to as evidence of hierarchical relationships between norms: article 103 UN Charter, jus cogens (Latin: ‘peremptory norms’) and obligations erga omnes (Latin ‘towards all’).

Article 103 UN Charter reads: ‘In the event of a conflict between the obligations of the Members of the United Nations under the present Charter and their obligations under any other international agreement, their obligations under the present Charter shall prevail’. It may be argued that this provision functions as a ‘supremacy clause’, elevating the UN Charter to a hierarchically superior position in the international legal system. While at first sight this seems to be the case, it should be noted that the practical effect of this provision is largely limited to the obligation to comply with UN Security Council resolutions contained in article 25, as there are few other specific and concrete obligations in the Charter. It should also be borne in mind that this provision functions more as a rule of precedence, very different to the consequences of a norm’s jus cogens status, for example.

Jus cogens norms are clear example of hierarchy in international law. These peremptory rules of international law are defined as rules ‘from which no derogation is permitted’. In the event of a conflict between a rule of jus cogens and another international rule, the jus cogens rule prevails and the other rule is void. Further, articles 40 and 41 of ARSIWA impose additional obligations on states in the event of serious violations of jus cogens norms, including a requirement to cooperate to bring about the end of the jus cogens violation and an obligation not to recognise as lawful any situation created as a result of such a violation. Established jus cogens norms include the prohibitions on genocide, slavery, torture, and racial discrimination.

Obligations erga omnes are defined as those owed “towards the international community as a whole”, with the result that “all [s]tates can be held to have a legal interest in their protection”. This seems to confirm the importance of such obligations, yet this concept does not imply a hierarchy between these and other norms. The label erga omnes serves to denote only an expansion in potential scope of actors who can invoke violation of the rule. This is a purely procedural device, which facilitates the enforcement of international rules which may not necessarily involve an injured state or to increase the likelihood of enforcement of rules deemed to be substantively important. Obligations erga omnes do not prevail over other rules of international law in the same way as jus cogens rules.

Advanced: The Relationship between Jus Cogens and Obligations Erga Omnes

The concepts of jus cogens and erga omnes are frequently taken together. Traditionally, it has been accepted that all jus cogens rules also have erga omnes status, but that the reverse was not necessarily true. Indeed, it is clear that both concepts serve to enhance the operation and level of protection for certain fundamental norms of international law. In the ILC’s recent work on jus cogens, there is further evidence of the close relationship between these two concepts. Here, the ILC suggested that the right to self-determination has also attained jus cogens status yet, in doing so, referred to ICJ decisions where only the erga omnes nature of self-determination was confirmed.

= Conclusions =

This chapter has explored the foundations of the doctrine of the sources in international law. In doing so, it has explained that the primary objective of this doctrine is to distinguish between rules that are part of the corpus of international law and those that are not. It has been explained that article 38 ICJ Statute constitutes an essential starting point for an account on the sources of international law, yet it does not paint a full picture. The relationships between international norms and their sources is complex and will be taken up further in subsequent chapters.

= Summary =

 * Sources of international law help to identify what the law actually is.
 * Article 38 ICJ Statute provides a starting point for the sources of international law, listing treaties, custom, general principles, and subsidiary means.
 * The development of international law is a dynamic practice, involving a range of actors, yet states remain at the centre of this practice.
 * There is no hierarchy between the sources of international law. Yet, there are some examples, particularly jus cogens, of hierarchical relationships between international norms.

= Further Reading =

 * S Besson and J d’Aspremont, The Oxford Handbook on the Sources of International Law (Oxford: OUP, 2017).
 * H Thirlway, The Sources of International Law (Oxford: OUP, 2014)


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Public International Law/Sources of International Law/Treaty Law

Author: Taxiarchis Fiskatoris and Marko Svicevic Required knowledge:

§ 1 History of International Law

§ 2 Nature and Purpose of International Law

Learning objectives:
 * § 2.2 Consent

Understand and define the term 'treaties' as international agreements in international law.

Explain key characteristics of treaties.

Understand how treaties are negotiated, drafted, and enter into force.

Understand how treaties are terminated or invalidated.

Examine how treaties are interpreted under the Vienna Convention on the Law of Treaties.

Explain what reservations entail and what their effect on treaties are.

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A. Introduction
Article 38(1) of the ICJ Statute names 'conventions, whether general or particular, establishing rules expressly recognized by… states' as the first source of public international law. More commonly known as 'treaties', they represent the most trusted and least controvertible avenue for States to express their consent to international legal rules. The United Nations Treaty Collection, which registers and publishes lists of treaties in accordance with Article 102 of the UN Charter, has over 250 000 treaties in its collection.

The basic international instrument of treaty law is the 1969 Vienna Convention on the Law of Treaties (VCLT), which is the main focus of this chapter. This chapter will therefore define and explain what treaties are and what role they play in international law, how treaties are negotiated and drafted, how they may be invalided or terminated, and how treaties are to be interpreted. As of June 2023, the VCLT has been ratified by 116 States. Most of its provisions have codified pre-existing customary international law, while other provisions have generated new custom. The VCLT only 'applies to treaties between States'. The rules regulating treaties between States and international organisations, and between international organisations have also been imprinted in a Convention, which has not yet entered into force. A third international convention with direct relevance to treaty law is the Vienna Convention on Succession of States in Respect of Treaties, which is in force but poorly ratified. All three have been drafted by the United Nations´ International Law Commission (ILC). The ILC is also responsible for several non-binding instruments which contribute to the overall study and scope of the law of treaties, such as the 2011 'Draft Articles on the Effects of Armed Conflicts on Treaties', the 2018 'Draft Conclusions on Subsequent Agreements and Subsequent Practice in Relation to the Interpretation of Treaties', and the 2021 'Draft Guide to Provisional Application of Treaties'.

1. Treaty law in context and of the times
Before going into more specific details on the rules of treaty law found in the VCLT, it is worth noting that the law of treaties is a complex and often delicate intervention in international law, given its very nature. Treaty law forms part and parcel of the 'nuts and bolts' of international law. As such, it is interwoven in almost every other discipline of international law. For example, while treaties are traditionally concluded between states, the role of non-state actors, broadly speaking has increasingly brought about questions. Non-governmental organisations, although without legal capacity to conclude treaties, have and continue to play a growing role in the drafting and negotiating of treaties. Likewise, as entities capable of legal personality, questions too arise as to what influence and obligations non-governmental organisations derive from general treaty law, such as those found in universal and regional human rights treaties. In turn this questions the broader role that non-state actors play in regard to the creation, development and clarification of the law of treaties. It is also worth noting that treaty law, although its progressive development and codification enhances clarity, is not without controversy nor ambiguity. Worthy of recollection is the fact that at the time the VCLT was negotiated and eventually adopted, not all states we see today were independent, and not all people's free from oppression of European and Western colonisation. Any consideration of the VCLT as a treaty regulating other treaties must therefore bear in mind its historical context. It has been well pointed out that, for example, applying a purely positivist approach to the VCLT would effectively if not entirely marginalise its role in international law.

These difficult issues more often than not transcend the VCLT itself, plaguing by extent the entirety of the law of treaties. Consider for example the effect of treaty law making long before the era of human rights and the adoption of the VCLT. The partitioning of Africa was in many ways effected through treaty law. These international agreements at the time were carefully negotiated with people's across regions. Despite what were in fact treaties which ultimately laid claim to territory and to the detriment of peoples of that territory, they were not necessarily directed at the various people's they were negotiated with, but rather as 'legal' symbols against rival European powers. While it is oftentimes easy to dismiss these practices and the corresponding effects of treaty law as relegated to the pages of history (once described as regulating 'common interests in international quasi-legislation, imposed on Africa from above'), the potential for these effects remains today. Indeed, while a fundamental principle of treaty law is that treaties are to be negotiated and implemented in good faith, there remain numerous cases even today where the law of treaties has fallen short of this expectation.

2. Defining treaties
Article 2(1)(a) of the VCLT defines a treaty as 'an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation'.

i. An international agreement concluded between States
'Every State possesses capacity to conclude treaties'. Although reference is made in the VCLT exclusively to States, the definition of treaties beyond the limited scope of the VCLT extends to international organisations, which have an autonomous international legal personality. Whether an international organisation has the capacity to conclude treaties depends on the rules of that organisation, and especially its constituent instrument. Until such a time as the 1986 Vienna Convention on the Law of Treaties between States and International Organisations or between International Organisations enters into force, which is admittedly very similar to the VCLT, such treaties are based on other sources of international law, in particular customary international law.

ii. In written form
For an international agreement to be called a treaty, it must be in written form, but not necessarily on paper. This is exactly the feature that renders treaties the most predictable and hence reliable source of public international law. Oral international agreements, as well as 'international agreements concluded between States and other subjects of international law or between such other subjects of international law' are not treaties per se, but they may still have legal effects. Such agreements are governed by other sources of public international law and not necessarily the provisions of the VCLT.

iii. Whether embodied in a single instrument or in two or more related instruments
Treaties are usually contained in a single document, but they do not always need to be. Exchange of letters (diplomatic notes), and even records of meetings between State representatives may constitute treaties if the intention of the parties was to create through them binding effects under international law.

iv. Governed by International Law
The intention to establish obligations and/or rights under international law is a key requirement for the characterisation of an international agreement as a treaty. States (and international organisations) are free to sign contractual agreements governed by national law (e.g. for leasing an embassy’s premises), which cannot be considered treaties. They are also free to enter international agreements not giving rise to obligations and/or rights under international law. Such agreements are often called “Memoranda of Understanding” (MoU). However, one should not pay too much attention to the headline of an agreement, as MoUs may in reality be proper treaties if the intention of the parties to give them binding effect under international law can be discerned. The intention to establish binding legal relations must be manifest within the text and context of the treaty.

v. Whatever its particular designation
As long as an international agreement fulfils the above four characteristics, it is from a legal point of view a treaty, whatever its name. Some of the most common names attached to a treaty are the following:

 * Article 38 of the ICJ Statute uses the term “Convention”. This is usually the name given to treaties prepared within an international organisation (e.g. UN Convention on the Law of the Sea; European Convention on Human Rights)
 * A “Protocol” is in most cases a treaty that supplements a pre-existing treaty with additional rights or obligations (e.g. Additional Protocols to the 1949 Geneva Conventions on International Humanitarian Law; Kyoto Protocol to the United Nations Framework Convention on Climate Change)
 * “Charter” is the label preferred for the constitutive treaties of international organisations (e.g. UN Charter, OAS Charter, OAU Charter, ASEAN Charter). The term may also designate a document that sets out a grant of rights or privileges (e.g. EU Charter of Fundamental Rights, African Charter on Humans and Peoples’ Rights).
 * The treaty establishing an international court or tribunal is often called a “Statute” (e.g. ICJ Statute; ICC Statute)
 * The word “Covenant” originates in religious scripts and traditionally refers to a solemn promise to engage in or refrain from a specified action. In international law it is used in the title of two major human rights conventions: International Covenant on Civil and Political Rights (ICCPR) and the International Covenant on Economic, Social and Cultural Rights (ICESCR), both adopted in 1966. It was also used in the case of the instrument establishing the League of Nations.
 * The label “Pact”, more common during the inter-war period, seems to connote a deal, that is not only legally but also morally binding (e.g. 1928 Kellogg-Briand Pact for Renunciation of War as an Instrument of National Policy)
 * The term 'Agreement' is used as an umbrella term covering both treaties and other instruments not meeting the VCLT criteria. In a narrow sense, the label 'agreement' is usually employed for treaties of a technical or administrative character between two States, or between a State and an international organisation.

3. Classification of treaties
Treaties establishing mutual rights and obligations between two parties are classified as bilateral. The great bulk of international treaties are bilateral in nature. A multilateral treaty is, on the other hand, a binding international agreement between many parties. A treaty between more than two but still not many parties can also be classified as plurilateral.

Most bilateral and plurilateral treaties merely create mutual rights and/or obligations for their parties, similarly to typical contracts of domestic law (contractual treaties). Although multilateral treaties also establish binding rights and/or obligations, most of them may eventually make, modify, elucidate and stabilize, or progressively develop international law more generally (law-making treaties). To be sure, several multilateral treaties purport to do so. In reality, the distinction between 'contractual treaties' and 'law-making treaties' is not always obvious.

4. Observance and application of treaties
The whole branch of international treaty law is premised on the fundamental legal principle 'pacta sunt servanda' (agreements must be respected). Article 26 of the VCLT enunciates that '[e]very treaty in force is binding upon the parties to it and must be performed by them in good faith'. A change of government does not release the State from its treaty obligations, unless the new government can raise a valid ground for the termination of the treaty. Besides, '[a] party may not invoke the provisions of its internal law as justification for its failure to perform a treaty'.

The flipside to the principle 'pacta sunt servanda' is the principle 'pacta tertiis nec nocent nec prosunt' (agreements neither injure nor benefit third parties). This is enshrined in Article 34 of the VCLT, according to which a 'treaty does not create either obligations or rights for a third State without its consent'. For third parties, an agreement to which they have not consented constitutes 'res inter alios acta' (things done among others). When parties to a treaty intend to impose an obligation on third parties, the latter must accept the obligation in writing. However, when parties to a treaty intend to afford a right to third parties, the consent of the latter is presumed as long as they do not raise an objection. If a treaty provision acquires the status of a customary rule of international law, it then becomes binding on third parties, even without their expressed consent.

The question of whether treaties are directly binding on individuals or other non-State actors is of marked importance in the context of international human rights law and international criminal law, but has yet to be doctrinally settled. Finally, unless otherwise agreed by its parties, treaties do not apply retroactively.

1. Drafting and Negotiation
Before adopting a bilateral treaty, States normally hold a series of meetings of diplomats and legal experts who negotiate and draft the terms of the treaty. Multilateral treaties, especially 'law-making treaties', are negotiated at international conferences, usually summoned by international organisations. At international conferences, where negotiations are more difficult due to the number of participants, States often debate on the basis of optional draft texts prepared by permanent or special committees of experts, such as the UN International Law Commission. The drafting process of a treaty may take many years. States are free to decide the place, time frames, set up, and rules of procedure of a conference. The VCLT only regulates that, unless participants decide otherwise, the minimum requirement for the adoption of the text of a treaty at an international conference is a two-thirds majority of the 'States present and voting'. In practice, States resort to voting only if consensus appears impossible.

2. Signature
Successful negotiations conclude with the adoption of the text of the treaty, and its recognition as authentic and definitive. The most common way for authenticating the finalised text of a treaty is its signature. Signing a treaty is an expression of a government’s intention to render the treaty binding for its State in due course. Nonetheless, the signature alone seldom establishes the consent of States to be bound by the treaty. Ordinarily, it is evident from the text of the treaty when no further steps are required.

In any case, the signature entails the legal obligation of the signatory 'to refrain from acts which would defeat the object and purpose of a treaty' until the ratification of the treaty, or until the signatory 'shall have made its intention clear not to become a party to the treaty'. To be sure, such interim obligation is vague and open to contradictory interpretations.

3. Consent to be bound
As a matter of rule, States establish on the international plane their consent to be bound by a treaty through the acts of 'ratification', 'acceptance', 'approval' or 'accession', although 'any other [agreed] means' are an option.

A second step after signature offers to States the required time to reconsider the treaty as a whole, eventually to submit it to parliamentary scrutiny and approval, or to enact respective legislation. It may take many years between signature and ratification, as there are no general time limits, unless the treaty specifies them. After all, States are under no obligation to ratify a treaty that they have signed.

Ratification of bilateral treaties occurs through the exchange of documents called 'instruments of ratification', which are issued for that scope by the competent authorities of the contracting States. A mere mutual notification of completion of all domestic procedures that give effect to the treaty may in routine cases replace the ceremonial exchange of instruments.

Treaties remain commonly open for signature until an arranged date. States that did not exist or sign the treaty before that date can still adhere to the treaty if the treaty or its parties allow it. The international act with which a State avails itself of the opportunity to become a party to a treaty previously adopted by other is called 'accession'. 'Accession' is an expression of consent to be bound by a treaty and hence it has the same legal effect as ratification. It usually happens after the treaty has entered into force, but, depending on the treaty, it can also take place before.

Ratification, acceptance, approval or accession of multilateral treaties is accomplished with the deposit of the respective instruments with the depositary. The depositary is one or more States, an international organisation, or the secretary-general of an international organisation, especially the United Nations. The depositary is normally designated by the treaty, among others to keep custody of the original text of the treaty, to collect all documents or communications relating to it, and inform respectively all parties concerned.

4. Entry into force
Ratification signals a State’s consent to be bound by a treaty. However, it does not signify an immediate assumption of the obligations and/or rights emanating from the treaty, which only begins when the treaty enters into force. After the ratification and before the entry of the treaty into force, the States must still 'refrain from acts which would defeat the object and purpose of a treaty, 'provided that such entry into force is not unduly delayed. Although it is very infrequent, States that have ratified a treaty may freely withdraw their consent to be bound before the treaty becomes operative. There may also be transitional clauses, dealing for instance with the permissibility of reservations, that take effect as from the adoption of the treaty. Most treaties contain a clause specifying when and how they will come into force.

Bilateral treaties often enter into force at the time the two parties exchange the ratification instruments, while treaties in simplified form can readily come into force immediately after signature. In case of an accession, the treaty enters into force for the acceding party on the date of the deposit of the accession instrument, or after a short period of time, if there was a corresponding provision with respect to the initial entry into force of the treaty.

5. Registration and Publication
Article 102 of the Charter of the United Nations requires that 'every treaty and every international agreement entered into by any Member of the United Nations… shall as soon as possible be registered with the Secretariat and published by it'. The provision pertains to both treaties that fulfil the aforementioned criteria, and other kinds of international agreements. Registration and publication with the United Nations Treaty Series is meant to eradicate the conflictual dynamic of secret diplomacy, and to enable public access. The UN Charter warns that unregistered international agreements cannot be invoked before any organ of the United Nations, including obviously the International Court of Justice. The practice of UN organs is less strict than the rule.

Registration should not be confused with a deposit of a ratification instrument with the Secretary-General of the United Nations. Treaties and international agreements can only be registered with the UN after their entry into force. The registration and publication duty extends to cases of treaty amendments. The registration by just one party to the treaty is adequate, while multilateral treaties are registered by their depositary. The UN does not impose any time constraints for registration. More importantly, 'non-registration or late registration… does not have any consequence for the actual validity of the agreement, which remains no less binding upon the parties'. Vice versa, the act of registration cannot turn a non-binding international agreement into a binding treaty.

i. Amendment
An “amendment” is a change of one or more treaty provisions, usually with the aim of updating or enhancing the treaty regime. Given that amendments affect all parties to the treaty, they must obtain the consent of parties to be bound by the amended provision. Thus, amendments are negotiated, signed, ratified, brought into force, registered and published. Some treaties require unanimity for an amendment to pass. If amendments can pass with a majority, parties that do not express their consent to be bound by the amendment remain bound by the previous provision, in conformity with the principles pacta tertiis nec nocent nec prosunt, and pacta sunt servanda. However, new parties acceding to the treaty accept the treaty as amended. Between the parties that have ratified the amendments or acceded to the amended treaty, and those that have not ratified them, it is the old provision that remains effective. The more parties to a treaty, the more difficult its amendment. This is why many multilateral treaties lay down specific amendment procedures and requirements, which may deviate from the above canon.

ii. Review, Revision
Some treaties provide an alternative 'review' or 'revision' procedure, which refers to updating the whole or part of the treaty at a new diplomatic conference with the participation of all parties to the treaty. Review or revision takes place after a provided number of years, or following a majority vote.

iii. Modification
Furthermore, 'two or more of the parties to a multilateral treaty may conclude an agreement to modify the treaty as between themselves alone if: (a) the possibility of such a modification is provided for by the treaty; or (b) … not prohibited by the treaty'. The original treaty provisions remain applicable between those few parties and all other parties. The modification must not affect the rights and/or rights of other parties under the treaty, and must not be incompatible with the object and purpose of the treaty as a whole.

1.Termination and Suspension
A treaty may be terminated or suspended in several ways described below. The termination permanently releases the parties from any obligation to perform the treaty. The suspension releases them from their treaty obligations temporarily. However, the termination 'does not affect any right, obligation or legal situation of the parties created through the execution of the treaty prior to its termination'. It is also immaterial when there exists a parallel customary rule of international law, which continues being biding on States. Besides, '[d]uring the period of the suspension the parties shall refrain from acts tending to obstruct the resumption of the operation of the treaty'.

i. Consent-based
A treaty may be terminated or suspended with the consent of all its parties. Likewise, if all parties to a treaty adopt a new substitute treaty, the earlier treaty impliedly loses its effect. However, the old treaty remains effective if not all of its parties adhere to the new one.

Should only some of the parties no longer feel like being bound by a treaty, they may denounce it or withdraw from it, but only if such a possibility is expressly allowed, implied by the nature of the treaty, or predicated on the established consensual intention of the parties. In any event, a party wishing to exit a treaty must give notice of its intention at least one year in advance. The term 'denunciation' is mostly used with reference to bilateral treaties, which are thus terminated. The term 'withdrawal' better describes the retreat from a multilateral treaty, which continues being in force among the rest of its parties.

There is also the possibility that the treaty itself contains an expiration date, or a clear goal, the achievement of which terminates the agreement. Nonetheless, a treaty does not terminate merely because it has not reached the required ratifications number for its entry into force.

ii. After a material breach of the treaty
The operation of a treaty can also be terminated or suspended as a consequence of its material breach. The VCLT defines a material breach as '(a) a repudiation of the treaty not sanctioned by the present Convention; or (b) the violation of a provision essential to the accomplishment of the object or purpose of the treaty'.

It should be noted though, that a material breach, regardless of its gravity, does not in itself terminate or suspend the treaty. It only entitles innocent parties to pursue the termination or suspension of the treaty in whole or in part, in accordance with a predetermined procedure. The consequences of a material breach depend on the bilateral or multilateral nature of the treaty. A breach of a multilateral treaty is more probable to temporarily render the treaty ineffective between the injured and the defaulting State, rather than leading to a comprehensive termination of the treaty.

Of course, the party that breached the treaty cannot invoke its own wrongdoing to terminate or suspend the treaty. Neither can a party pursue the termination or suspension of a treaty invoking the material breach of another treaty. Besides, 'treaties of a humanitarian character', including human rights treaties, cannot be terminated or suspected on such grounds. If a material breach of a treaty causes harm to a State, secondary rules of State responsibility apply, irrespectively of whether the harmed State pursues the termination or suspension of the breached treaty.

iii. Due to a fundamental change of circumstances
On demand of several drafting States, the VCLT did not exclude the termination of or withdrawal from a treaty due to a fundamental change of circumstances which has rendered the execution of treaty obligations unexpectedly onerous or unfair. However, in order to keep it in line with the primordial principle of the sanctity of treaties (pacta sunt servanda), the VCLT sets a high threshold for the application of the so-called rebus sic standibus (so long as things stand) clause. The ICJ has also consistently upheld a very restrictive approach.

Thus such a pleading can only be made if cumulatively

a) the change is fundamental;

b) could not have been foreseen;

c) has 'radically' transformed the extent of obligations still to be performed under the treaty into something different from what originally agreed; and

d) the specific circumstances at the time of the conclusion of the treaty constituted an essential basis of the consent of the parties to be bound by the treaty.

Additionally, this ground of termination is inapplicable to treaties establishing a boundary, as well as unavailable to any party that induced the fundamental change by not performing its duties towards the other treaty parties. 'A boundary established by treaty thus achieves a permanence which the treaty itself does not necessarily enjoy'.

iv. Due to supervening impossibility of performance
A less controversial ground for termination/withdrawal is 'the permanent disappearance or destruction of an object indispensable for the execution of the treaty', which unexpectedly renders its performance not simply onerous or unfair, but impossible. If the supervening impossibility of performance is temporary, it can only lead to the suspension of the treaty. Once again, if a party contributed to the occurrence of such a situation, it cannot itself pursue the termination/suspension of the treaty on this ground. The submergence of an island under the sea level, or the natural desiccation of a river as an effect of climate change may be scenarios giving rise to such a termination/suspension ground.

v. Because of an armed conflict
The VCLT sets forth that '[t]he severance of diplomatic or consular relations between parties to a treaty does not affect the legal relations established between them by the treaty except insofar as the existence of diplomatic or consular relations is indispensable for the application of the treaty'. However, the effects of armed conflicts on treaties fall outside the scope of the Convention. The ILC has attempted though to prepare a set of non-binding Draft Articles on the matter. The general principle is that the outbreak of an international armed conflict, or a non-international armed conflict in which governmental authorities take part, may terminate or suspend a treaty as between States parties to the conflict or as between a State party to the conflict and a State that is not; but not necessarily.

When the treaty itself is silent on the matter, the answer can primarily, but not exclusively, be sought in

'a) the nature of the treaty, in particular its subject matter, its object and purpose, its content and the number of parties to the treaty; and

b) the characteristics of the armed conflict, such as its territorial extent, its scale and intensity, its duration and, in the case of non-international armed conflict, also the degree of outside involvement'.

However, there is a number of treaties, 'the subject matter of which involves an implication that they continue in operation, in whole or in part, during armed conflict'. Such are, by way of illustration, multilateral 'law-making treaties', treaties creating permanent regimes, especially treaties establishing boundaries, treaties for the international protection of human rights, treaties on international criminal justice, treaties relating to the international protection of the environment or to international watercourses and aquifers, treaties creating international organisations, treaties relating to diplomatic and consular relations, treaties relating to the international settlement of disputes, and of course treaties regulating the conduct of hostilities.

vi. Other grounds
Art 64 of the VCLT postulates an additional termination ground, namely the emergence of a new peremptory norm of general international law (jus cogens). In such an event, 'any existing treaty which is in conflict with that norm becomes void and terminates'. A jus cogens norm is defined by the VCLT as 'a norm accepted and recognized by the international community of States as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character'. To be sure, the exact content of such norms remains unclear. If the supervening jus cogens norm is not in contrast but with a treaty clause that may stand independently from its context, the norm only severs the said clause without implications for the rest of the treaty.

Art 42 of the VCLT suggests that the enumerated termination/suspension grounds are exclusive. It is debatable though whether by means of customary international law, or as forms of implied consent, desuetude or obsolescence constitute additional grounds. The former refers to a consistent practice of the parties to a treaty, that runs counter to their treaty obligations. The latter refers to the expiration of the treaty through disuse.

Another debatable termination ground is the full performance of a treaty, when the treaty itself does not explicitly provide for such eventuality.

Last but not least, it is only logical that a bilateral treaty comes to an end when one of the two State-parties loses its international legal personality, unless of course there is a successor State.

2. Invalidity
Under specific circumstances, treaties may lose their validity, although this occurs very rarely. Invalidity has different legal consequences compared to termination. While the latter releases the parties from their treaty obligations from the point of the termination on, invalidity exonerates the injured parties from the legal effects from the point of conclusion of the treaty. Practically, acts having been performed in execution of a void treaty before its invalidation may need to be reversed. However, claims of reversal cannot be made by a party that has generated the grounds for the invalidity.

i. Absolute grounds for invalidity
The VCLT enumerates three absolute grounds for invalidity, which automatically render the treaty null and void:

a) when the consent of a State to be bound by the treaty has been a product of coercion of a representative of a State through acts or threats directed against him or her;

b) when the consent is a product of coercion of the State itself by the illegal threat or use of force 'in violation of the principles of international law embodied in the Charter of the United Nations'. The last words exclude any legal threat or use of force after an authorisation of the UN Security Council or in self-defence. Besides, only the military use of force gives rise to invalidity. A treaty cannot be invalidated if a State has been compelled to ratify it, say, under the pressure of economic sanctions, or the political pressure from a former coloniser. Such forms of pressure have merely been condemned by the drafters of the VCLT in a non-binding declaration annexed to the Final Act of the Vienna Conference;

c) Thirdly, a treaty is void if, at the time of its conclusion, it conflicted with an existing jus cogens rule.

Even if the act of coercion pertained to a single treaty clause, or even if only a single treaty clause is against a pre-existing peremptory norm, it is still the whole treaty that automatically becomes null and void.

ii. Relative grounds for invalidity
The VCLT also lists five relative grounds for invalidity, which do not render the treaty void ab initio, but voidable. Put differently, relative grounds do not immediately nullify the treaty, but rather give to an affected State the right to retrospectively annul its consent to be bound by that treaty. This would practically mean the nullification of a bilateral treaty, or a withdrawal of the victim State from a multilateral treaty with retrospective effect. In the latter scenario, though, the rights and obligations of other treaty parties would remain unaffected. Contrary to the consequences of absolute grounds, there is the possibility for severing the clauses to which the relative grounds are related, instead for nullifying the whole treaty.

Relative grounds, potentially invalidating the consent of an affected State, are the following:

a) A 'manifest' violation of 'fundamental' internal law provisions regarding competence to conclude treaties. The VCLT goes on to clarify that '[a] violation is manifest if it would be objectively evident to any State conducting itself in the matter in accordance with normal practice and in good faith'. The term 'fundamental' points to constitutional or equivalent rules.

b) Omission by a State representative to observe specific restrictions on authority to express the consent of his/her State, on the precondition that the other negotiating parties had been duly notified.

c) An error that 'relates to a fact or situation which was assumed by [the affected] State to exist at the time when the treaty was concluded and formed an essential basis of its consent to be bound by the treaty. Had the error been foreseeable or caused by the affected State itself, it cannot be invoked as a ground for invalidity. Likewise if the error relates only to the wording of treaty text.

d) Fraudulent conduct of another negotiating State.

e) Corruption of a representative of the affected State, directly or indirectly by another negotiating State.

1. Reservations
Article 2(1)(d) of the VCLT defines a reservation as 'a unilateral statement, however phrased or named, made by a State, when signing, ratifying, accepting, approving or acceding to a treaty, whereby it purports to exclude or to modify the legal effect of certain provisions of the treaty in their application to that State'. Reservations to treaties are one way in which States express their disagreement with certain provisions and exclude their legal effect to such States. In this way, a State that wishes to be party to a specific treaty may nonetheless adopt and ratify the treaty without compromising the entirety of the instrument because of one or several provisions it disagrees with. For such reasons, reservations provide a compromise whereby, especially for multilateral treaties, they can achieve widespread adoption and acceptance by numerous States.

While reservations are a useful tool for States in excluding or modifying a treaty's legal effects, there are certain cases where reservations are prohibited. In principle, three situations prohibit reservations:

 * if the reservation is incompatible with the object and purpose of a treaty
 * if the reservation is prohibited by the treaty
 * if the treaty provides only for specified reservations and the reservation is question fall beyond the scope of such specified reservation.

These limitations to reservations which States may make are for the most part reasonable. For example, reservations which are incompatible with the object and purpose of a treaty are prohibited in that, if made, could render the entirety or very logic behind the treaty void.

Treaties focusing on issues of climate change and the environment are one example where reservations are often explicitly prohibited. For example, Article 25 of the Kyoto Protocol provides that '[n]o reservations may be made to this Protocol'. Another example of a treaty which prohibits reservations is Article 120 of the Rome Statute of the International Criminal Court.

Where a treaty expressly provides for reservations, there is no need for other States party to the treaty to accept the reservation made by one of the State parties. In some cases however, State parties to a treaty may need to accept or even object to reservations made to such treaty. If, for example, there is a limited number of negotiating States and the object and purpose of the treaty requires its application to all the parties as an essential condition of their consent, then reservations made to such treaty need to be accepted by all parties. Another example where reservations needs to be accepted is where the treaty in question is a constituent instrument of an international organisation, in which case, a competent organ of that organisation needs to accept the reservation.

Reservations and objections to reservations may be withdrawn at any time and do not require the consent of any State which had previously accepted such reservation.

2. Interpretative declarations
Another unilateral statement which a State can make when joining a treaty is an interpretative declaration. Interpretative declarations are statements in which a State indicates or clarifies what it understands to be the scope or nature of specific treaty provisions. Interpretative declarations do not modify the provisions of a treaty but may later be followed by other States in how they too interpret certain provisions of that treaty.

Beyond the standard interpretative declaration, a State may also make a conditional interpretative declaration. Such a declaration has the effect that a State does not wish to be bound by certain provisions unless a specific interpretation is accorded to those provisions. Conditional interpretative declarations are therefore subject to the same rules as reservations.

Although the distinction between reservations, interpretative declarations and conditional interpretative declarations may seem simple, in practice their distinction is not as easy. States sometimes use ambiguous language when entering these unilateral statements, ultimately making it difficult to determine their intention.

1. Interpretative authorities
One of the starting points in discussing treaty interpretation is precisely who has the authority to interpret treaties. Given they are legal texts distinct from the domestic laws of States, it is necessary to understand both who may interpret them and precisely how they are to be interpreted. In principle, the application of a treaty implies interpretation; since it would not be possible to apply the provisions of a treaty without first reading and interpreting its provisions. On this basis therefore, all entities concerned with the treaty in question engage in its interpretation. Subjects of international law who therefore have the competence to interpret treaties and their provisions include:

 * States
 * International organisations and their organs
 * International courts, tribunals and forums
 * Domestic courts, tribunals and forums

2. General rule of Interpretation
Article 31 of the VCLT provides the general rule of interpretation of treaties and reflects customary international law. The rules embodied in Article 31 of the VCLT adopt a multifaceted approach to interpreting treaties. Treaties are first and foremost to be interpreted in good faith and the ordinary meaning of terms are to be used, in context and in light of a treaty's object and purpose. The interpretation of a treaty includes its context, which in addition to the main text, preamble and annexes also includes other agreements which relate to the treaty made between the parties in connection with the treaty, or, an instrument made between one or more parties in connection with the treaty accepted by other parties as an instrument to the treaty.

In addition, further context taken into account when interpreting the provisions of a treaty are the subsequent agreement and subsequent practice of State parties regarding the interpretation of a treaty. In other words, subsequent agreement and subsequent practice in the application of the provisions of a treaty, may clarify how they interpret it and may even indicate they consider such an interpretation effective for purposes of apply its provisions. It also makes perfect sense that given the wording of Article 31(1), special meanings are given to terms only if the parties so intended. In practice, most treaties usually start off with a section defining terms used with the treaty, in this way clarifying how such terms are not only understood in the context of the treaty, but how they are applied throughout its provisions.

One of the reasons behind the interpretation of treaties suggested by Article 31 is that, naturally by examining the very text and context of a treaty, it is presumed that a treaty constitutes an authentic expression of the intentions of its parties. Only by examining the treaty itself can one ascertain the intention of its drafters.

3. Other theories of treaty interpretation
In addition to those rules of interpretation mentioned above, there exist a number of theories of treaty interpretation.

 * Teleological interpretation: requires that the meaning of words and terms be interpreted in light of the object and purpose of a treaty. In such cases, a teleological interpretation aims to give effect to the overall aims and objectives of a treaty.
 * Systematic interpretation: requires a treaty to be interpreted with the ordinary meaning of words and that all parts of a treaty as well as corresponding documents produced between the parties be taken into account. Such documents would include the negotiation and drafting history of a treaty.
 * Textual interpretation: requires that the ordinary meaning of words be used to interpret treaties, that such meaning be clear, and that upon interpretation, does not lead to unreasonable or absurd outcomes.
 * It is worth mentioning that other theories of interpretation may differ to those found in the VCLT. Briefly, there is no concrete position as to which theory one should adopt when interpreting treaties. Some authors take the VCLT as a point of departure, whereas others consider either the complimentary or exclusive position of other theories of interpretation.

4. Supplementary means of interpretation
Beyond the general rule of interpretation in Article 31 of the VCLT, Article 32 provides supplementary means of interpretation. According to Article 32, certain elements may be used in furthering the precise meaning of provisions if upon application of the rules of interpretation in Article 31 prove unsatisfactory (to the extent that ambiguities remain or the application of Article 31 leads to manifest absurdity or unreasonableness).

Supplementary means of interpretation under Article 32 most commonly include the preparatory work of a treaty, including documents related to negotiation history between the State parties and drafting history of the treaty. Preparatory works are usually available to the negotiating parties, thereby excluding unilateral sources and confidential sources, that may not necessarily have been introduced or made available to other negotiating States parties.

Supplementary means of interpretation carry less weight as they are in effect meant to complement and clarify the application of Article 31.

Further Readings

 * Anthony Aust, Modern Treaty Law and Practice (3rd ed, 2013 CUP)
 * Enzo Cannizzaro (ed), The Law of Treaties: Beyond the Vienna Convention (2011 OUP)
 * Christine Chinkin, Third Parties in International Law (1993 Clarendon Press; OUP)
 * Olivier Corten and Pierre Klein (eds), The Vienna Conventions on the Law of Treaties: A Commentary (2011 OUP)
 * Oliver Dörr and Kirsten Schmalenbach (eds), Vienna Convention on the Law of Treaties: A Commentary (2nd ed, 2018 Springer)
 * Richard Gardiner, Treaty Interpretation (2nd ed, 2017 OUP)
 * Paul Gragl and Malgosia Fitzmautice, `The Legal Character of Article 18 of the Vienna Convention on the Law of Treaties´, (2019) 68(3) ICLQ 699
 * Duncan B. Hollis (ed), The Oxford Guide to Treaties (2nd ed, 2020 OUP)
 * Alina Kaczorowska, Public International Law (Routledge, 2012), 3rd ed.)
 * Jan Klabbers, The Concept of Treaty in International Law (1996 Martinus Nijhoff)
 * Robert Kolb, The Law of Treaties: An Introduction (2016 Edward Elgar)
 * Ulf Linderfalk, On the Interpretation of Treaties: The Modern International Law as Expressed in the 1969 Vienna Convention on the Law of Treaties (2007 Springer)
 * UN Treaty Section of the Office of Legal Affairs, Treaty Handbook, (Rev ed, 2012 UN Publications)
 * Benjamin Mulamba Mbuyi, Droits des Traités Internationaux: Notes de Cours à l'Usage des étudiants en Droit (2009 L'Harmattan)

Conclusion

 * Summary I
 * The law of treaties is a fundamental aspect of international law regulating the entry into, conclusion, validity application, and interpretation of treaties. The VCLT codifies much of customary international law on the law of treaties.
 * A treaty is, under Article 2(1)(a) of the VCLT 'an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation'.
 * Ordinarily, treaties are negotiated, drafted and signed by their parties. Following adoption, a treaty then goes through the ratification process before it comes into force.
 * Treaties can be amended, modified and reviewed. Treaties can also be terminated. Grounds for suspension or termination include, by consent of the parties, following a material breach of the treaty, based on a fundamental change in circumstances, due to supervening impossibility of performance or because of an armed conflict.
 * Treaties can be invalidated on two broad grounds: Absolute grounds for invalidity and relative grounds for invalidity. Absolute grounds for invalidity include: the conclusion of a treaty is a product of coercion of a representative of a State through acts or threats directed against him or her; when the consent is a product of coercion of the State itself by the illegal threat or use of force 'in violation of the principles of international law embodied in the Charter of the United Nations'; if, at the time of its conclusion, it conflicted with an existing jus cogens rule. Relative grounds for invalidity include: a “manifest” violation of “fundamental” internal law provisions regarding competence to conclude treaties; omission by a State representative to observe specific restrictions on authority to express the consent of his/her State, on the precondition that the other negotiating parties had been duly notified; an error that “relates to a fact or situation which was assumed by [the affected] State to exist at the time when the treaty was concluded and formed an essential basis of its consent to be bound by the treaty”; had the error been foreseeable or caused by the affected State itself, it cannot be invoked as a ground for invalidity. Likewise if the error relates only to the wording of treaty text; fraudulent conduct of another negotiating State; corruption of a representative of the affected State, directly or indirectly by another negotiating State.
 * In so far as reservations concern, they are unilateral statements made during the negotiation, signing, adoption or accession of State party to a treaty modifying or excluding legal effect of certain provisions of that treaty.
 * Regarding the interpretation of treaties, Articles 31 and 32, considered to reflect customary international law, provide the rules of interpretation. Article 31 provides the general rule of interpretation, and includes that terms be assigned their ordinary meaning and that treaty provisions be interpreted in good faith.

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Public International Law/Sources of International Law/General Principles

Author: Craig Eggett

Required knowledge: Sources of International Law; others ?

Learning objectives: To understand the background to article 38(1)(c) ICJ Statute; how general principles can be identified; what general principles (can) do in international law.

A. Introduction
Article 38(1) ICJ Statute’s list of generally-accepted sources of international law concludes with sub-paragraph (c)’s ‘general principles of law’. This source of law has received considerably less attention than treaties and customary law. For example, article 38 (1)(c) has never been explicitly relied on by the Court as a basis of a decision, being referenced in only a handful of proceedings. Further, academic discussion on this source of law had, until rather recently, been rather sparse. The discourse on general principles received a significant boost when, in 2017, the ILC decided to include the topic on its programme of work. Since then, the Commission has produced three reports and a set of draft conclusions on general principles and there has been a notable increase in scholarly attention on the topic. This chapter aims to provide an overview of the core aspects of the ongoing discussion on general principles in international law. To that end, it is structured around three main questions: (1) what kind of norms are general principles? (2) how are they ascertained? and (3) what functions do they perform? These questions overlap to an extent, yet they provide a basic logical structure to examine general principles and their place in the international legal system.

B. The Nature of General Principles
There has been considerable theoretical disagreement as to what exactly is meant by ‘general principles of law’. In other words, what exactly is it that we are talking about when we refer to the norms in article 38(1)(c) ICJ Statute? This question has implications for the identification and functioning of general principles, in addition to touching upon some fundamental aspects of the international legal system as such. To add further complexity to this question, it is also the case that the term ‘general principles’ is used in a more rhetorical sense to underline the importance or general scope of application of these norms. So, as an initial point, it is important to clarify that this chapter is concerned with general principles in the technical sense of article 38(1)(c) ICJ Statute.

That being said, the range of positions and perceived importance of general principles vary greatly. These norms could be seen as fundamental building blocks of the international legal system, as technical procedural norms, or merely as a tool for the interpretation of treaties and customary law. The ILC’s first draft conclusion provides a starting point for this question. It reads: ‘The present draft conclusions concern general principles of law as a source of international law.’ As indicated in the previous sub-chapter, authors may disagree as to what exactly it means to refer to a ‘source’ of law. Yet, this draft conclusion, as the ILC explains, confirms the legal nature of general principles of law. The following sections examine this legal nature by considering, first, the historical background of general principles in the international legal system and, second, the conceptual aspects of the normative classification of general principles and their relationship with other norms and concepts.

C. History and Origins of General Principles in International Law
Indeed, both the wording and history of the ICJ Statute confirm that general principles, whatever they may be, have a role as applicable law in the settlement of disputes. The drafting of article 38 ICJ Statute is based on the corresponding provision of the PCIJ Statute, which contains identical wording in relation to general principles, noting that ‘[t]he Court shall apply general principles of law recognized by civilized nations’. This wording – shall apply – confirms the role of general principles as an applicable source of law. The notion that general principles of law are a source available to judges in adjudicating a dispute has a history extending further back than the drafting of even the PCIJ Statue. For example, references to ‘principles’ as a source of applicable law were included in the Arbitral Procedure Regulations 1875, the First Hague Convention establishing the PCA, and the Convention Relative to the Creation of an International Prize Court 1907. While differing in their precise construction, the references to ‘principles’ illustrates that early practice recognised a role for a source of international law beyond treaties and custom.

Further, early arbitral practice suggests a role for general principles in international law. For example, in the Walfish Bay Boundary case, the arbitrator was required to determine the applicable law in the proceedings due to the absence of such a provision in the compromis. In doing so, the arbitrator explained the approach taken and noted that the issues at hand ‘must be solved in conformity with the principles and positive rules of public international law, and, where they fail, in conformity with the general principles of law’. As an example of the consideration of a specific general principle, in the Pious Fund case, the Tribunal was required to consider a previous decision rendered by the Mexico-United States Mixed Claims Commission. In doing so, the Tribunal found that the principle of res judicata (Latin: ‘a matter judged’), which has its origins in domestic systems and Roman law, was applicable in international law and so governed the decision in question.

In the drafting of the PCIJ Statute, the Advisory Committee of Jurists discussed the draft of article 38, including the phrasing of what would eventually become article 38(1)(c) ICJ Statute. The original draft of article 38 proposed by the Chair of the Advisory Committee, Baron Descamps, referred to ‘the rules of international law as recognised by the legal conscience of civilized nations’. This formulation suggests a more concrete category of norms – rules – derived from domestic systems, representing a departure from some earlier references to ‘principles of justice and equity’. In their discussion of Descamps’ draft, the members of the Advisory Committee debated the role that this third source of law would play and the powers that it would grant to the Court. Positions on the nature and operation of this source differed greatly, with a primary concern being the degree of discretion that would be given to the Court to develop international law. There was opposition to the idea that the Court could take an active role in the development of new international law rules in the absence of state consent, despite Descamps himself viewing the provision as a limit on such discretion. The formulation was changed into to its final form following a proposal by Root and Phillimore at the 15th Meeting of the Advisory Committee. Throughout the discussions of the Advisory Committee, there was broad agreement that the purpose of this provision was to make available to the Court a source of applicable law that could be relied upon in the absence of any applicable treaty or customary rules. The legal nature of general principles as a source of applicable law was apparent from the outset.

D. General Principles, Rules, and other Norms
The debates of the Advisory Committee on the formulation of the general principles provision point towards a more conceptual issue: that of the normative classification of general principles. From the initial starting point that general principles are a source of applicable law, questions arise as to how exactly these norms may be used. A central issue is whether general principles, in and of themselves, can be a source of obligations in international law. Further, following from the notion that general principles typically apply in the absence of treaties and custom, there is frequently a conflation between general principles and other categories of norms or concepts in international law.

On the question of whether general principles can be a direct source of obligation, the decision by the Advisory Committee to use the term ‘principle’ in place of the original ‘rule’ could suggest that general principles are different kind of norm, distinct from concrete rules of law. Indeed, there are authors who argue that general principles are broader and vaguer norms that do not impose direct obligations by provide a more general framework for the interpretation and application of rules and discretion to judges. In a similar vein, some would argue that general principles have natural law overtones and links to broader values or moral considerations. Conversely, some authors would argue that general principles, like the other sources of law, are capable of granting rights and imposing obligations. There are others, still, that view general principles as some sort of in-between; as a type of transitory norms between values and concrete rules or as a form of ‘inchoate custom’. Despite these contrasting positions, it seems clear that international courts and tribunals view themselves as being capable of recognising rights and obligations beyond treaties and customary law. A prominent example of this is the development of many procedural rules of international law, which courts and tribunals have frequently recognised as general principles owing to their presence in domestic law and foundation in certain established ‘legal maxims’.

As a category of norms of general international law, it can be a challenge to demarcate general principles from custom, as well as from jus cogens (Latin: 'peremptory norms') and other notions, such as values, equity, and justice. The distinction between general principles and custom can be particularly difficult to draw. Both are unwritten sources of (typically) general application. Further, it seems perfectly possible that there could exist customary rules and general principles that have similar or identical content, as has been recognised in the case of treaty and customary rules. Indeed, the ILC confirms this in its draft conclusion 11 on general principles, which reads:

1. General principles of law, as a source of international law, are not in a hierarchical relationship with treaties and customary international law.

2. A general principle of law may exist in parallel with a rule of the same or similar content in a treaty or customary international law.

3. Any conflict between a general principle of law and a rule in a treaty or customary international law is to be resolved by applying the generally accepted techniques of interpretation and conflict resolution in international law. It has been suggested that general principles could have a supportive relationship to customary rules, aiding in their formation and interpretation. Yet, there are key differences in both the ascertainment and functions of custom and general principles. While custom is anchored in the practice and views of states, the formation of general principles involves a more pronounced role for courts and tribunals in the examination of domestic systems and notions of legal logic.

As for jus cogens, it was acknowledged by the Special Rapporteur on the topic that the reference to ‘general international law’ in article 53 VCLT includes general principles in the sense of article 38(1)(c) ICJ Statute. Indeed, the ILC expressed support for the idea that general principles of law could attain jus cogens status. Given the nature of established jus cogens norms as clear prohibitions on certain conduct, this could be seen as further evidence that general principles are a source of concrete rights and obligations. While there may be a relationship between general principles and the notion of jus cogens, it should be noted that the label ‘jus cogens’ denotes a certain elevated status that can be assigned to a norm, regardless of its source, and not a source of law in and of itself.

Finally, it seems that there is a close relationship between general principles and notions such as equity, justice, and the values of the international community. It is commonly recognised that there exist certain basic values upon which the international legal system is built, such peace and security, respect for human rights and humanity, and sustainable development. These broad values, it has been argued, may lead to the creation of general principles of law. There appears to be a significant degree of interaction between general principles and the broader values of the international legal system. Indeed, it seems logical that support for a general principle may be evidenced by its consonance with the basic objectives of the system as a whole and with fundamental ideas of legal logic.

E. Identifying General Principles
Turning now to the more practical question of how to identify a general principle. The text of the ICJ Statute itself provides little guidance on this matter. It is broadly agreed that the term ‘civilized nations’ should be discarded. Indeed, the ILC has confirmed that the phrasing ‘is anachronistic and should no longer be employed. In today’s world, all nations must be considered to be civilized.’ Going further, in a Separate Opinion in North Sea Continental Shelf, Judge Ammoun asserted that the term “is incompatible with […] the United Nations Charter”. Once the term ‘civilised nations’ is discarded, we are left with the requirement that a prospective general principle must be ‘recognised’. From this rather unhelpful starting point, two issues arise: (1) whose recognition is relevant? and (2) how can it be determined that there is sufficient recognition of a general principle?

I. Recognition by ‘the community of nations’
The issue of whose recognition is relevant for the identification of a general principles touches upon a fundamental question in international law, namely: is the creation of international law solely the prerogative of states? Indeed, traditionally, international law concerned solely states. It was states that were seen as the only participants in international law, becoming bound by an international rule only when they had given their consent to it. The ILC seemed to stay broadly in line with this position with its second draft conclusion, which reads: ‘For a general principle of law to exist, it must be recognized by the community of nations’. Before settling on the formulation “community of nations”, the ILC considered a number of terms, including “international community” and “international community of States”. The Commission explained that it adopted this phrase because of its use in article 15(2) of the ICCPR, which, because of the widespread membership of this treaty, signifies broad acceptance of this terminology. How this term will be interpreted and what significance will be attached to it is yet to be seen, but it is clear that this formulation seeks to maintain the position of states as central actors in the creation of international law.

II. Methodology for the Recognition of General Principles
Many of the ILC draft conclusions on general principles are concerned with the approach to be taken when identifying these norms. The approach set out by the Commission is predicated on an initial distinction between two categories of norms. According to draft conclusion 3, ‘General principles of law comprise those: (a) that are derived from national legal systems; (b) that may be formed within the international legal system’. This distinction between general principles derived from domestic law and those that develop on the international level is consonant with previous accounts of general principles of law, and the ILC differentiates between the approaches to the ascertainment of each of these categories.

1. General Principles Derived From National Systems
Similar to previous attempts, the ILC sets out a two-stage approach to this category of general principles. Draft conclusion 4 reads:

To determine the existence and content of a general principle of law derived from national legal systems, it is necessary to ascertain:

(a) the existence of a principle common to the various legal systems of the world; and

(b) its transposition to the international legal system. The first of these steps is anchored in the idea that comparative law serves as a foundation for the ascertainment of general principles in international law. With such a requirement, issues arise as to the scope and content of such an analysis. The ILC seeks to provide some guidance on this in the next draft conclusion, which explains that:

1. To determine the existence of a principle common to the various legal systems of the world, a comparative analysis of national legal systems is required.

2. The comparative analysis must be wide and representative, including the different regions of the world.

3. The comparative analysis includes an assessment of national laws and decisions of national courts, and other relevant materials. In its explanation of this draft conclusion, the Commission explains that the comparative assessment need not involve the examination of every legal system of the world. Instead, the ILC proposed a more ‘pragmatic’ approach involving consideration of a representative sample of both the ‘different legal families and the regions’ of the world. Indeed, such an approach would be a welcome departure from the practice of courts and tribunals when engaging in comparative law, as there has typically been reliance on just a handful of predominantly European legal systems. It is of course crucial that a norm of general application find broad support in a range of legal traditions and different parts of the world.

Following the ILC’s approach, it is not sufficient to merely identify a norm common to domestic legal systems. Indeed, as was noted in the South West Africa Advisory Opinion, rules of domestic law are not transposed ‘lock, stock and barrel, ready-made and fully equipped’ into international law. Therefore, there is an additional step of transposition into international law. According to the ILC, ‘[a] principle common to the various legal systems of the world may be transposed to the international legal system in so far as it is compatible with that system’. In order to determine this compatibility, the Commission sets out that a prospective general principle must be compatible with the fundamental principles of international law, such as sovereignty or basic principles in certain fields like law of the sea. Further, the ILC explained that it is necessary that ‘the conditions exist to allow the adequate application of the principle in the international legal system. This serves to ensure that the principle can properly serve its purpose in international law, avoiding distortions or possible abuse’. This requirement seems logical given the fundamental differences in the nature and structure of international law – as a decentralised and horizontal legal system – when compared with national systems.

2. General Principles Formed Within the International Legal System
When it comes to the identification of general principles with origins in the international legal system, the ILC states that ‘it is necessary to ascertain that the community of nations has recognised the principle as intrinsic to the international legal system’. In its Second Report, the Commission explained that a general principles may be seen as intrinsic to the international legal system if (1) it is widely recognised in treaties and other international instruments, (2) it underlies a general treaty or customary rule, or (3) it is inherent in the basic features and fundamental requirements of the international legal system. The first two of these indicate a close relationship between general principles and the other sources listed in article 38 ICJ Statute, suggesting that the repeated reference to a norm in treaty law or custom can in turn create a general principle. As for the final alternative, the ILC provided examples such as uti possidetis juris (Latin: ‘as you possess under law’) or the requirement that states consent to jurisdiction.

As can be seen from the work of the ILC, evidence for the existence of a general principle can be found in a range of different instruments and other sources. Further, in its draft conclusions, the ILC specifically reiterated the role of the subsidiary means – judicial decisions and academic teachings – in the determination of general principles of both categories.

F. The Functions of General Principles
Already at the drafting stage of article 38, it was suggested that general principles would have primarily a role to play where there was no applicable treaty or customary rule. This ‘gap-filling’ function is also a prevalent feature of scholarly accounts on general principles. Indeed, in its first draft conclusion on the matter the ILC explains that ‘[g]eneral principles of law are mainly resorted to when other rules of international law do not resolve a particular issue in whole or in part’. The Commission confirmed that this ‘essential function’ of general principles was to avoid situations of non liquet (Latin: ‘it is not clear’).

In addition to this, the ILC emphasised that general principles contribute to the coherence of the international legal system, a function that has also been advanced in literature. The Commission elaborated that general principles, ‘may serve, inter alia: (a) to interpret and complement other rules of international law; (b) as a basis for primary rights and obligations, as well as a basis for secondary and procedural rules’. The first of these functions seems to follow logically from the references to the links between general principles and the other sources of law in the context of ascertainment. In this regard, the ILC makes explicit reference to the rules of systemic interpretation referred to in article 31(3)(c) VCLT, confirming that this provision’s reference to ‘rules of international law’ includes general principles. Finally, the ILC’s confirmation that general principles can form a basis for both primary and secondary rules is consonant with the aforementioned legal nature of general principles as source of international law. It should be noted that it is in the development of secondary procedural rules that general principles have been identified as the most relevant. Scholarly accounts of general principles couple them with ‘international due process’ and ‘procedural’ norms, and international practice confirms that courts and tribunals most frequently make reference to general principles when attempting to answer a procedural question not covered by treaty or customary rule.

G. Conclusion
This chapter has provided an overview of the basic conceptual aspects of general principles as a source of international law, in light of ongoing debates about their place in the international legal system. It is clear that general principles are a recognised source of international law and that there are many potential instruments and concepts that can be consulting during their ascertainment. It remains to be seen what exactly the full potential of these norms will be, but there is scope for greater reliance on general principles to enhance the functioning of the international legal system as a whole.

Summary

 * General principles of law are recognised, alongside treaties and customary law, as a source in article 38(1)(c) ICJ Statute.
 * The debate on general principles has intensified since being included on the ILC’s programme of work in 2017. The ILC has produced three reports and a set of draft conclusions on general principles.
 * It is commonly argued that there is a distinction between general principles that arise from domestic law and those that emerge in the international legal system. The ILC proposes a different approach to ascertainment for these two categories.
 * The principal and established function of general principles is to fill gaps in the law left by treaties and custom. Other functions, include fostering coherence in international law and developing (primarily) procedural rules of law.