China's claims through the continental shelf: Under the UN Convention on the Law of the Seas, state territory may extend to the continental shelf, while the exclusive economic zone may be extended 200 miles from the coastline. This however, serves only as a basic scheme. Foreign territory, which extends into the continental shelf, would adjust the size of any adverse territorial claims. Fascist China's claims in the South China Sea are based on its continental shelf. However, this creates problems because its territorial claims extend into the claims of other states, which are in turn based upon their own continental shelves and outlying islands. Thus in this area, basing territory exclusively upon the continental shelf brings no resolution to any of the underlying claims. Exclusive reliance on the Law of the Sea produces overlapping claims.
China, Vietnam and Taiwan claim all of the Spratly Islands, while the Philippines, Malaysia, and Brunei claim portions.
Colonial France exercised control over the islands from 1933 to 1939, and Imperial Japan took possession of the islands during WW2.
China's claims to the islands are based mainly upon ancient evidence, including discovery and sightings going back as far as the mythical Xia dynasty. After WW2, it claims the islands were returned to it under both the 1943 Cairo Conference and the 1945 Potsdam Proclamation. It further claims the islands based on the 1952 San Francisco Allied Peace Conference when Imperial Japan's renounced rights to Taiwan, the Spratlys, and other islands occupied during the war.
The claims of other states are based more on proximity (the islands are 1000 miles away from China's coast, and often visually within the distance of many of the Southeast Asian countries), actual use and control. The continental shelves of many of the states in SEA also extend to include...