China first claimed straight baselines in its 1958 Declaration on the Territorial Sea, which said that the baseline for measuring the breadth of China's territorial sea is composed of the straight lines connecting the base points on the mainland coast and on the outermost points of its coastal islands.

In its Working Paper on Sea Area within the Limits of National Jurisdiction submitted to the UN Seabed Sub-Committee in 1973, China suggested that an archipelago or an island chain consisting of islands close to each other should be taken as an integral whole in defining limits of the territorial sea around it. Article 3 of the Law of the People's Republic of China on the Territorial Sea and the Contiguous Zone says that the method of straight baselines composed of all the straight lines joining the adjacent base points should be used to draw the baselines of China's territorial sea. China has been consistent in using straight baselines to delimit its territorial sea when it comes to an archipelago or an island chain consisting of islands close to each other that can be taken as an integral whole.

In fact, China has been insisting on using the straight baselines system since 1958, and exercising sovereign rights over the waters within the baselines. The United States and other countries only oppose China's practice to set 12 nautical miles as the width of its territorial sea and have no objection to its suggestion that an archipelago or an island chain should be taken as an integral whole in defining limits of the territorial sea around it. China's declaration on the territorial sea, measures to define limits of the territorial sea and state practice to exercise sovereign rights in the above-mentioned waters have been recognized by other countries. This means China already had historic sovereignty over the waters in question before the UN Convention on the Law of the Sea took effect.

In 1996, China announced its first batch of base points and baselines for its territorial sea, delineating baselines of most coastal sections of the mainland and the Xisha Islands. The baselines of the Xisha Islands have been delineated based on China's historic sovereignty over the waters within the baselines.

China has not delineated the baselines of the territorial sea of the Zhongsha, Dongsha and Nansha Islands. It will delineate the baselines of these islands, especially the Nansha Islands, on the basis that an archipelago or an island chain consisting of islands close to each other can be taken as an integral whole and its historic sovereignty over these islands.

The Half Moon Shoal is about 118 kilometers northeast of China's Commodore Reef and more than 110 km from the Palawan Island of the Philippines. As a result, there is a dispute between China and the Philippines over the demarcation of waters in the South China Sea. In accordance with the UNCLOS, if Beijing and Manila cannot immediately reach an agreement on maritime demarcation, they should make efforts to work out effective temporary arrangements based on the spirit of understanding and cooperation. In this context, China has always advocated negotiations to seek a peaceful resolution.

The fact is that, Beijing and Manila have agreed to cooperate to resolve the dispute through negotiations. In 2002, China and the Association of Southeast Asian Nations, including the Philippines, signed the Declaration on the Conduct of Parties in the South China Sea, emphasizing their determination to settle the disputes in the South China Sea through friendly negotiations and dialogue. But of late Manila has been creating trouble in the South China Sea. By claiming that China's Half Moon Shoal and its adjacent waters are part of its exclusive economic zone and carrying out "law enforcement activities" in the disputed waters, the Philippines is violating the declaration and blatantly infringing on China's territorial sovereignty. In other words, Manila's claims are illegal and invalid.

China is a signatory to the Convention on International Trade in Endangered Species of Wild Fauna and Flora and has also enacted the Wildlife Protection Law. If the Chinese fishermen have violated the convention in the waters under China's jurisdiction, it should be the Chinese-not the Philippine-court's responsibility to punish them. By detaining the Chinese fishermen in China's waters, the Philippines has infringed on China's territorial sovereignty and should be held accountable for it in an international court of law.

The author is a professor of international law and marine law at the Party School of the Central Committee of the Communist Party of China.