The Power to Define Offenses Against the Law of Nations

Abstract

Congress has the power to “define and punish...Offenses against the Law of Nations.” This clause empowers Congress to punish offenses universally recognized under international law, such as piracy, but it also confers the power to “define” offenses against the law of nations. Punishing an offense must entail defining it, so what does “define” add?

This article provides an answer. The Constitution’s text and structure, early constitutional history, and modern foreign relations doctrine all suggest that Congress has the power to define offenses against the law of nations that preexisting international law does not forbid. This power is broad: Congress may pass laws criminalizing private conduct that violates international law and private conduct that the United States has an international duty to punish. Congress can also prohibit private conduct if it is unclear whether it has a duty under international law, or if the United States is alone in thinking that it has such an international duty.