<jats:p><jats:disp-quote><jats:p>When the President does it, that means that it is not illegal.</jats:p><jats:p>Richard M. Nixon</jats:p></jats:disp-quote></jats:p><jats:p>Customary international law is part of federal common law. Federal common law is binding on every executive branch official, including the President. Congress can by statute create a different rule, however, because federal common law is interstitial; it fills in gaps between statutes and gives way when an inconsistent law is enacted. Consequently, with congressional authorization, the Chief Executive can disregard any norm of customary international law. But in the face of congressional silence, he is required to respect a clearly defined and widely accepted norm of customary international law. I consider this position, elaborated in a recent article in the <jats:italic>North-western Univernty Law Review</jats:italic>, to be most consistent with traditional separation-of-powers principles and also the soundest functional approach.</jats:p>