U.S. already bound by "Common Heritage of Mankind" principle through customary international law

However, the United States is likely already bound by the “common heritage of mankind” doctrine under principles of customary law.⁶¹ Customary law is generally thought of as widespread systematic practice that is backed by opinio juris, or the belief that one is acting in accordance with legal obligation.⁶² Because these are not objectively measureable qualities, customary law is not always easy to identify. The Convention, including its provisions regarding the “common heritage of mankind” principle, is considered to represent the customary law of the seas, supported in part by its widespread ratification.⁶³ Under general principles of international law, customary law is binding on all states, including the United States.⁶⁴ The United States, thus, is bound by those provisions of the Convention that are deemed customary law, which likely include the “common heritage of mankind” principle.