The rule of law promises protection and recourse against the arbitrary exercise of power. Not only must those who govern rule with law, they must themselves be ruled by law. The rule of law requires reflexivity — law’s rule of those who rule with law and in its name. This essay explores the conditions for the realization of law’s rule. Philosophical explorations of the rule of law ideal largely focus on principles of legality — the formal, procedural, and institutional aspects of the ideal — but these discussions are seriously incomplete because they ignore fidelity, the ethos of law. Fidelity underwrites and makes possible law’s rule. The rule of law is robust in a polity only when it is characterized by widespread fidelity, that is, only when its members, and not merely the legal or ruling elite, take responsibility for holding each other and especially law’s officials to account under the law. Law’s rule rests on the commitments, practices, and institutional infrastructure of a polity-wide network of mutual accountability. It opposes all forms of sovereignty, insofar as they ground accountability ultimately in an unaccountable accountability-holder.