U.S. would have stronger ground to challenge China's "Nine-Dashed Line" and push for multilateral solutions as a party to UNCLOS
China claims as their “historical waters” more than three-fourths of the South China Sea, delineated by the so-called nine–dash line, pictured below.
These claims are generally considered outrageous by everyone except the Chinese, who have kept the justification for them (and the nature of the claims themselves) ambiguous. The Obama administration has done an admirable job of standing with other Southeast Asian countries trying to resist China’s pressure in these territorial disputes. The administration has called for a multilateral process based on the rule of law, rather than the bilateral approach Beijing prefers.
But the U.S. position would be much stronger if the United States could simply say that, “The U.N. Law of the Sea Convention should govern this dispute.” As Secretary of State Hillary Clinton explained in her recent testimony before the Senate Foreign Relations Committee:
I’m sure you have followed the claims countries are making in the South China Sea. Although we do not have territory there, we have vital interests, particularly freedom of navigation. And I can report from the diplomatic trenches that as a party to the convention, we would have greater credibility in invoking the convention’s rules and a greater ability to enforce them.
The Chinese get a lot of mileage in conversations with Southeast Asian nations from the United States not being a party to the convention. (“How can the Americans tell us that Law of Sea Convention applies when they haven’t even ratified it?”) That’s why Secretary Clinton was joined by five Republican predecessors, who penned an op-ed in the Wall Street Journal this past month asking for Senate ratification.