Rising tensions in the South China Sea are a tired front of great power competition.  Since President Barack Obama’s “pivot to Asia,” there has been renewed attention on growing Chinese naval power and influence, which stands to challenge the U.S. status as the world’s preeminent naval force.  Despite a clear and obvious interest in maintaining a favorable global oceans regime, the United States has not ratified the United Nations Convention on the Law of the Sea (UNCLOS), the principal international instrument governing the use of the oceans.  Instead, the United States argues that ratification is unnecessary because UNCLOS “embodies” customary international law.  This Note explores the legal context of U.S. nonmembership and analyzes its implications along three axes:  U.S. rights and obligations, access to effective dispute settlement mechanisms, and the ability to shape future developments of the law of the sea.  It concludes that relying on customary international law without being party to UNCLOS is not sufficient to guarantee the foundation of the U.S. Freedom of Navigation policy.  On the contrary, ratification is in the U.S. best interest:  it would lock in a favorable status quo, lend the United States credibility to meaningfully challenge divergent behavior, and offer a venue to shape the future of the law of the sea.