When Vietnam and Malaysia submitted a joint claim for the outer limits of their continental shelves in the South China Sea to the UN Commission on the Limits of the Continental Shelf in 2009, China objected. In response, it submitted a nine-dashed, or U-shaped, line map of its claim in the South China Sea to the United Nations. The Chinese statement and the U-shaped line provoked official objections, including notes to the United Nations from Vietnam and Indonesia.

The U-shaped line has since become a target for international criticism, with many scholars questioning its legal basis and Beijing’s activities within it, including its habit of driving away foreign ships exploiting oil and gas resources within the U-shaped line and its annual summer fishing ban in parts of the South China Sea since 1999. Due to their disagreements with China, many foreign governments and scholars have asked for the Taiwanese government’s explanation of the original meaning behind the U-shaped line (which was first officially introduced by the Republic of China in 1947).

But with the issue’s rising international profile and political sensitivity, Taipei would rather keep silent on its interpretation of the U-shaped line. This is compounded by Taiwan’s frustration that it is excluded from most venues for managing the South China Sea, such as those between China and ASEAN on the implementation of the 2002 Declaration on the Conduct of the Parties in the South China Sea, and the more recent negotiations on a China-ASEAN Code of Conduct. To ask Taipei to accept the political risks of taking a position on the U-shaped line—especially one more in line with the legal positions of the other claimants than with those of China—without access to any of these mechanisms to manage the disputes is unfair.

The Philippine government, with the support of the United States and Japan, filed a case before an arbitral tribunal under the United Nations Convention on the Law of the Sea (UNCLOS) in 2013, hoping to resolve its disputes with China by legal means. The tribunal ruled in 2016 that China’s purported claims to historic rights within the U-shaped line have no legal basis. But the ruling did not tackle the legality of the U-shaped line itself, in all its potential interpretations. To do so would have been outside the jurisdiction of the tribunal. This led to mistaken reporting by the international press that the U-shaped line is inconsistent with UNCLOS.

While Taiwan has not officially clarified its position, the original purpose behind the U-shaped line when it was published in 1947 seems to have been as an island attribution line. It marked an area of the South China Sea within which the government of the Republic of China claimed sovereignty over all islands and expected their return following World War Two. Maritime rights have evolved since that time, especially in 1982 with the introduction of the exclusive economic zone in UNCLOS. Faced with those evolving concepts, the U-shaped line was bound to provoke arguments. But if the line refers only to the islands within it, then it does not run counter to UNCLOS.

In the early 1990s, the government of Taiwan organized a task force to draft a new Law on the Territorial Sea and Contiguous Zone. At that time, some Taiwanese scholars argued that Taiwan should claim the seas within the U-shaped line as historic waters. But the Legislative Yuan rejected such an enlarged concept of the U-shaped line because it was inconsistent with the UNCLOS definition of historic waters. As a result, Taiwan’s Law on the Territorial Sea and Contiguous Zone, which was adopted in 1998, is completely in accordance with the regulations of UNCLOS, despite Taiwan not being a party to the treaty. Since that time, the government has made no move to claim historic waters within the U-shaped line. And that basic policy has been consistent across both Kuomintang and Democratic Progressive Party administrations.

Despite China’s attempts to entitle the seas within the U-shaped line with a new concept of historic rights, the line itself is not inconsistent with UNCLOS. Given the rising tensions, it is natural that the meaning of the line has caused nervousness in the region, especially since the intensification of the disputes in 2009. But the mere existence of the U-shaped line is not to blame—it has since 1947 been a claim to sovereignty over the islands in the South China Sea.

About Chen Hurng-Yu

Chen Hurng-Yu is Honorary Professor at National Chengchi University and Tamkang University in Taiwan. He was previously professor in the Department of Diplomacy and International Relations and director of the Graduate Institute of Southeast Asian Studies at Tamkang University, and served as director of the Center for Southeast Asian Studies at National Chi Nan University and a research fellow at National Chengchi University.