How is it possible that the idea of sovereignty still features in law and legal philosophy? Sovereignty is normally taken to refer to absolute power. Yet modern law assumes that power is exercised by officials constrained by legal rules and the rule of law. This essay argues that a closer look at sovereignty and law shows that the first impression is correct: law and sovereignty are mutually exclusive. Philosophically speaking, sovereignty is and has always been incompatible with the rule of law and with constitutional law itself. Sovereignty and constitutional government are mutually exclusive.