In small groups, norm enforcement is achieved through mutual punishment and reward. In large societies, norms are enforced by specialists such as government officials. However, not every public cause is overseen by states, for instance those organized at the international level. This paper shows how non-governmental norm enforcement can emerge as a decentralized equilibrium. As a first stage, individuals voluntarily contribute to a non-governmental agency that produces an incentive system. The second stage is the provision of a public good on the basis of private contributions. The incentive system increases contributions by means of public approval or disapproval of behavior. It is shown that, even in large populations, non-governmental norm enforcement can be supported in a non-cooperative equilibrium of utility-maximizing individuals. This result is in sharp contrast to those obtained in the standard situation of voluntary provision of an intrinsic public good which – without altruism or related motives – is eroded by free-riding. Reliance on altruistic behavior is not required in supplying the second-order public good ‘norm enforcement’ in large societies.