4.13 Freedom of speech has been characterised as one of the ‘fundamental values protected by the common law’. Heydon J has observed that ‘there are many common law rights of free speech’ in the sense that the common law recognises a ‘negative theory of rights’ under which rights are marked out by ‘gaps in the criminal law’.
4.14 The High Court of Australia has stated that freedom of speech is ‘a common law freedom’ and that it ‘embraces freedom of communication concerning government and political matters’:
The common law has always attached a high value to the freedom and particularly in relation to the expression of concerns about government or political matters … The common law and the freedoms it encompasses have a constitutional dimension. It has been referred to in this Court as ‘the ultimate constitutional foundation in Australia’.
4.15 In relation to defamation, the common law defence of qualified privilege has been extended on the basis of the constitutionally protected freedom of communication, discussed below. In Lange v Australian Broadcasting Corporation (Lange), the High Court determined that, as the development of the common law in Australia cannot run counter to constitutional imperatives, the common law rules of qualified privilege should properly reflect the requirements of ss 7, 24, 64, 128 and related sections of the Australian Constitution.
4.16 Freedom of speech is not absolute. Even the First Amendment of the United States Constitution has been held not to protect all speech: it does not, for example, protect obscene publications or speech inciting imminent lawless action. Australian common law has long recognised limits to free speech, for example, in relation to the criminal law of incitement and conspiracy, and in obscenity and sedition law.
Nationwide News v Wills (1992) 177 CLR 1, 31.
Attorney-General (SA) v Corporation of the City of Adelaide (2013) 249 CLR 1,  (Heydon J). See Ch 2.
Monis v The Queen (2013) 249 CLR 92,  (French CJ).
Lange v Australian Broadcasting Corporation (1997) 189 CLR 520, 566, 571.
Brandenburg v Ohio 395 US 444 (1969).