Other countries could follow China's lead and push for more restrictive interpretation of military passage that limits U.S. military freedom of navigation

Here is another critical point: The 163 parties to Law of the Sea Convention could choose to change the convention’s terms at any time. After all, the convention as it stands today is not the same as earlier versions. In fact, there is a marked trend now toward coastal states claiming more jurisdiction over their adjacent waters than the current convention recognizes.

Chances are that any new version of the convention called for by Brazil, China, and other emerging coastal powers would push in favor of a more “Chinese” definition of exclusive economic zone transit rights. They might call for a larger zone with more limited rights for noncoastal states.

That would be a disaster for the United States. America, with the most powerful Navy in the world and trade links that span the globe, needs full freedom of navigation in the world’s oceans. If we do not ratify the Law of the Sea, we will have a very hard time stopping that kind of change, and the longer we wait, the weaker our position will be. We should lock in the beneficial rules—the ones that we helped draft—now.

As it is the United States follows customary maritime law. But customary law can also change over time in ways we cannot control. If the world’s other coastal states such as China start claiming that U.S. military assets can’t transit their exclusive economic zones without permission, that practice could enter customary maritime law. Then the United States would have a hard time arguing that it was going to ignore customary maritime law and instead follow the terms of a treaty that it had never ratified.