We analyze the optimal relationship between the public and private enforcement of property rights for the case of rival and nonrival goods. Exclusion is interpreted as a costly activity, which allows it to endogenize the distinctions between public and club goods on the one hand and between private and common-pool goods on the other. We characterize optimality conditions for the private provision of rival and nonrival goods, characterize optimal enforcement policies, and compare the solutions with other institutional alternatives.