As the chairman of the panel at the 1985 ASIL Annual Meeting on the question “May the President Violate Customary International Law?” I must confess that the issue that originally troubled me when I suggested this topic for discussion remains securely hidden in the shadows of the debate. Yet I think it is of central importance. The reason it has remained obscure, despite its significance, is that it is an extraordinarily difficult intellectual puzzle. My brief purpose here is to bring it into the light, not to try to solve it.