U.S. sovereignty has more to lose by not being party to the treaty
Today's opponents, including Ayotte, DeMint, and Portman, focus on two issues. First, they argue, the treaty is an unacceptable encroachment on U.S. sovereignty; it empowers an international organization -- the International Seabed Authority -- to regulate commercial activity and distribute revenue from that activity. Yet sovereignty is not a problem: During the 1994 renegotiation, the United States ensured that it would have a veto over how the ISA distributes funds if it ever ratified the treaty. As written, UNCLOS would actually increase the United States' economic and resource jurisdiction. In fact, Ayotte, DeMint, and Portman's worst fears are more likely to come to pass if the United States does not ratify the treaty. If the country abdicates its leadership role in the ISA, others will be able to shape it to their own liking and to the United States' disadvantage.
The sovereignty costs associated with the Convention are grossly overstated primarily because many of these costs have already been accepted by the United States. In addition, the U.S. stands to gain sovereignty over 4.1 million square miles of territory by acceeding to the treaty.