The Philippines filed an arbitration case in 2013 against China before the Permanent Court of Arbitration to challenge, among other things, Beijing’s nine-dash line claim to most of the South China Sea. Although the legal character of the nine-dash line is not a new dispute between China and its neighbors, it has become a significant foreign policy and international legal headache for another South China Sea claimant: Taiwan. This is because China claims that its nine-dash line is a successor to the U-shaped line map issued by the Republic of China (ROC) in 1947. By doing so, China both asserts its sovereignty over Taiwan and diverts some international political pressure from Beijing to Taipei.
Against this background, Taiwan faces international pressure over whether it should explicitly clarify and define the legal character of the U-shaped line in accordance with the UN Convention on the Law of the Sea (UNCLOS). For Taiwan, the interpretation of the U-shaped line is not merely a legal issue. It involves how Taiwan balances its strategic relationship with both the United States and China. If the Permanent Court of Arbitration either invalidates the Chinese nine-dash line or narrows the possible legal interpretations of the line, it will provide other claimants and partners like the United States with powerful political leverage against Beijing. This in turn has led to pressure on Taiwan to clarify its own claim of the U-shaped line.
But is such a clarification really necessary? Taiwan has never explicitly made excessive maritime claims in the South China Sea, and is in fact constrained from doing so by its own actions.
Since the issuance of the 1947 map, Taiwan has never claimed a historical entitlement to all the waters within the U-shaped line. As a matter of international law, this means that Taiwan already adheres to the legal principle of mare liberum, which stresses freedom of navigation and that the ocean cannot be occupied. Therefore, it is hard to imagine Taiwan would claim the waters within the U-shaped line as its exclusive territorial.
Taiwan’s legal options vis-à-vis the U-shaped line are also constrained because in 2005 Taipei suspended the 1993 Policy Guidelines for the South China Sea. The guidelines” were an executive order issued by the Executive Yuan (Cabinet). Their original function was to coordinate each ministry’s functions relevant to the South China Sea and consolidate them under one legal instrument. The preamble of the guidelines says, “(The ROC) has jurisdiction over the maritime area within the historical waters line and enjoys all the rights and interests within it.” Although the preamble does not explicitly identify this “historical waters line,” there is no line but the U-shaped line on Taiwan’s official map of the South China Sea. By suspending the guidelines in 2005, Taiwan discontinued its claims to historical waters. Legally speaking, though “suspension” implies that the guidelines might be restored in the future, the longer they remain suspended, the more difficult such restoration will be. Even were the guidelines and their provisions for a historical waters line restored, they would be attacked under the principle of estoppel in international law.
The illustration of the U-shaped line on an official map, “The First ROC Territorial Baseline and Territorial and Contiguous Zone Lines,” also constrains Taipei’s legal options. There is a brief footnote on the map noting, “All of the islands and rocks of the Spratly Islands within the traditional U-shaped line are ROC territory.” The map therefore suggests Taiwan claims only territorial sovereignty over the islands and rocks within the U-shaped line, not historical rights or sovereignty over the waters within the line. If Taiwan’s government regarded historical rights and waters as an indispensable interest within the U-shaped line, there would be no reason to exclude mention of them from the map. This does not necessarily prevent Taiwan from taking action to claim historical rights and waters in the future, but it does provide ammunition against Taipei were it to do so.
It is also difficult for Taiwan to make excessive maritime claims in the South China Sea because any changes to the nation’s South China Sea policy garner significant public scrutiny. Even though the two major political parties in Taiwan have somewhat different positions on South China Sea policy due to their conflicting attitudes toward Beijing, neither has any incentive to substantially change the policy status quo for fear of being punished, either by constituents or international actors (especially China and the Unites States).
A series of responses by Taipei in the South China Sea over the last two years have placed the issue under even greater public scrutiny. When the government of President Ma Ying-jeou proposed the South China Sea Peace Initiative, issued a Statement on the South China Sea, and took actions to bolster its argument that Itu Aba (Taiping) Island is legally an island and not a rock, it was criticized by politicians and commentators who accused it of a willingness to cooperate with China. However, under such intense domestic social scrutiny, it will be politically impossible for the government in Taipei to make assertive claims based on the U-shaped line or even cooperate with Beijing.
Scholars usually list four potential meanings for the U-shaped line: 1) A territorial sea or boundary line; 2) A historical waters line; 3) A historical rights line; and 4) A claim to the islands within it. By its own state practice, Taiwan has, for now, largely constrained itself to only the islands claim.
At present, Taiwan has no reason to explicitly interpret the legal character of the U-shaped line. Its long-term state practices have implicitly reassured the United States that Taiwan is not cooperating with China while at the same time remaining acceptable to Beijing. If the ruling in the South China Sea arbitration case goes against China, Taiwan and the United States should be even more careful not to upset the current balance. For now, maybe saying nothing is the best means for Taiwan to contribute to stability in the South China Sea.