This article examines the role of coercion in grounding a prima facie duty to obey the positive law. I argue that there is at least a weak prima facie duty to obey the positive law in a minimally effective and just legal system. The fact that a norm holds positive legal status within a minimally effective and just legal system gives people presumptive reason to believe that the norm is a salient and reasonable means of social coordination and therefore that they have pro tanto reason to follow it. Coercive sanctions may bolster the salience of social norms by giving people incentive to follow them. They also make it more likely that an agent’s decision to follow a particular norm will be reasonable, by creating the prospect that the reasons supplied by the sanctions will override any deficits in the salience or reasonableness of the norm itself. A legal system with strong coercive enforcement is therefore more likely than a less coercive system (other things being equal) to present its subjects with both prima facie and pro tanto moral obligations. This reliance on coercion, however, carries a significant moral hazard, since it may bootstrap inefficient or unreasonable norms into a position of epistemological and moral weight.