I can't tell if you are bringing this up because you are criticizing the Americans for refusing to join and be bound by the UN Convention on the Law of the Sea

I can't tell if you are bringing this up because you are criticizing the Americans for refusing to join and be bound by the UN Convention on the Law of the Sea or if you are accusing the Chinese of violating their treaty commitments. If it's the former, I don't think the US will be joining it any time soon. US military grand strategy depends on its ability to deploy marines with its navy anywhere swiftly in the world. That's why the Panama Canal was built: to allow the US Navy to swiftly move between Oceans to reallocate force posture. This is why the United States rejected the UNCLOS court juristiction over its boobytrapping the coastal regions around Nicaragua - the US refuses to be bound by this international law (the other major one, I would suggest, is the International Criminal Court/Rome Statues). If you mean the second, the Chinese have argued that this is a territory dispute, in which case UNCLOS itself (article 299, IIRC) agrees it has no authority. Certainly UNCLOS is a major aspect to understanding the South China Sea situation, and should be linked.