Here, in a short, easy to understand article, by Professor Jay L. Batongbacal of the University of the Philippines College of Law, is some very useful background on the legal status of the Scarborough Shoal in the South China Seas.
Prof Batongbacal is director of the university’s Institute for Maritime Affairs and Law of the Sea; he is, in others, words, an expert, and he suggests that that Scarborough Shoal may have a special status that differs from the Paracel and Spratly Islands.
I certainly do not doubt Prof Batongbacal’s qualifications as an expert on the law of the sea, and he may be right that the USA is, somehow, obliged to take more active steps should China build a base, à la Mischief Reef, in the Scarborough Shoal, but I’m not sure I can see how the US might translate an obligation into some actions sufficient to deter China without coming dangerously close to provoking armed conflict. It may be a legal obligation but it could also be a strategic trap.
The problem is that China is bullying the Philippines and it may get away with it because the ASEAN nations are not united in how to respond to China, and America is, right now, confused and distracted.
This is another of those times when I wish Canada had more, newer, better warships in our Pacific fleet.