International Law and Constitutional Interpretation: The Commander in Chief Clause Reconsidered

The Commander in Chief Clause is a difficult, underexplored area of constitutional interpretation. It is also a context in which international law is often mentioned, but not fully defended, as a possible method of interpreting the Constitution. This Article analyzes why the Commander in Chief Clause is difficult and argues that international law helps resolve some of the problems that the Clause presents. Because of weaknesses in originalist analysis, changes over time, and lack of judicial competence in military matters, the Court and commentators have relied on second-order interpretive norms like congressional authorization and executive branch practice in interpreting the war and foreign affairs powers of the President. International law can itself function as a second-order interpretive norm, in many ways similar to other forms of congressional authorization or executive branch practice. But because it is mediated in unique ways—by other countries and within our own domestic political system—international law is an especially compelling way to resolve problems with judicial competence and changes over time. International law also makes a powerful contribution to an originalist understanding of the Commander in Chief Clause: the Constitution explicitly vested control over war-related questions of international law with Congress, not the President.