The principles of good faith and bad faith are “fundamental to more or less every legal system on a world scale” but not, it might seem, to American constitutional law. Thousands of cases have applied these principles in fields ranging from contracts to bankruptcy to nuclear disarmament. Outside the criminal procedure and qualified immunity contexts, however, the language of good faith and bad faith rarely surfaces in constitutional doctrine. Nor have these ideas received focused attention in the secondary literature. Constitutional law, in these ways, has been an enclave of good faith and bad faith exceptionalism.