Is there a moral duty to obey the law? Or more precisely, do citizens of any modern state have a general duty to acknowledge its authority to determine for them, for action guiding purposes, whether certain kinds of conduct are morally permissible, required, or forbidden? Moral contractualism, I contend, entails that citizens of a liberal democratic state do have such a duty.

Treating others morally often requires agents to act collectively. But even agents who accept the moral necessity of collective action will sometimes disagree over the specification of the ends to be achieved, and the means for doing so. I argue that a liberal democratic state (and only such a state) can justifiably claim the authority to resolve such disagreements, which it does mainly by enacting and applying laws. Obedience to democratic laws expresses respect for others' autonomy.

In defending these claims, particular attention is paid to the problem posed by disagreement over the design of democratic decision procedures, conflicts between democratically enacted laws and individual rights, and conflicts of rights. Civil disobedience, conscientious objection, and over-inclusive laws are also addressed.