Since the islands belong to SOMEBODY and that somebody has territorial limits around the islands, this is NOT a "freedom of the seas" Issue. Bt the way the So has refused to sign the Law of the Seas treaty.
One thing is clear: these islands or whatever they are, are NOT US property. Therefore, US laws will NOT apply if China is shut out of expoitation of the islands. If it is about oil, US companies have made some of the greater oil messes on this planet and are clearly not better than anyone else.
So if it is about fish, then it mush be because the US thinks Vietnam, the Philippines, Taiwan or whoever will have more strict fishing laws than the Chinese. If the fish are a resource, it makes no sense for any nation to overfish.