On the other, in the early 20th century, China mainly occupied the major islets of the two archipelagoes, such as the Yongxing Island and the Taiping Island, because in light of the law of the sea in force at that time, a country did not have to occupy every islet, rock and reef to claim its sovereignty over an archipelago, especially when the rest of the islets were faraway and hard to be reached.

China did not often reiterate its sovereignty over the islands before World War II, because it was universally acknowledged that a country does not have to frequently claim its sovereignty when there is no strong sovereignty request from other countries. Such a principle has been widely adopted in solving territorial disputes, including the 1928 Island of Palmas Case, 1931 Clipperton Island Arbitration and the 1933 Legal Status of Eastern Greenland.

Although UNCLOS is now the law in force to regulate maritime activities, it cannot deny China's historical rights over the Nansha Islands. China's traditional maritime border took shape in 1947, 47 years before UNCLOS came into force in 1994, when concepts such as continental shelf and exclusive economic zone were not yet known. Just as Chao Kuo-tsai, an expert in international law at Taiwan-based "National Chengchi University", has said, vested right is restricted by the law contemporary with it and cannot be withdrawn by laws coming into force later.

Moreover, according to UNCLOS, a coastal country enjoys certain rights over its exclusive economic zone, but such rights are restricted to the natural resources and the country has no sovereignty title over the islands in the region. Therefore, the surrounding countries in the South China Sea cannot use the exclusive economic zone as an excuse to forcibly occupy China's Nansha Islands, even though some of these islands are less than 200 nautical miles from their coastal baselines.

After UNCLOS came into force, some surrounding countries in the South China Sea have been using its articles beneficial to them to claim sovereignty and jurisdiction rights over the islands, and thus intensifying the disputes. The intensified disputes make the implementation of UNCLOS questionable.

Kriangsak Kittichaisaree, former legal officer in Thailand's Ministry of Foreign Affairs, has said: "The 1982 Law of the Sea Convention merely set a 'goal' to be achieved but is silent as to the method to be followed to achieve it. It restricts itself to setting a 'standard', leaving it to the States themselves, or to the Courts, to endow this standard with specific content".

By manipulating the shortcomings of UNCLOS, the surrounding countries have forcibly occupied China's Nansha Islands, are hindering China's offshore oil drilling, and driving away and even sinking Chinese trawlers. Confronted with such threats, China should consider its own situation before enforcing UNCLOS, clearly stipulating its rights over its exclusive economic zone and continental shelf. This is a basic right of a sovereign country and the right way to defend the country's sovereignty and maritime interests.