Although much legal scholarship discusses the meaning of the religion clauses of the U.S. Constitution, very few articles analyze the ways in which state regulation affects actors' incentives to engage in religious behavior. Yet the question of how a law influences religious behavior is important for determining whether various laws are desirable, and whether they violate constitutional constraints. This article draws on recent economic models of religious organization to analyze the ways in which laws affect the behavior of religious groups. Religious groups produce collective goods for their members, and the effect of laws can be analyzed by examining how they modify the payoffs members receive for cooperating or free riding. The article examines the use of laws to establish religious groups, to subsidize them with cash or tax benefits, to provide accommodations for them, to provide symbolic support for them, to provide secular substitutes for the collective goods they produce, and to regulate disputes between members. The article also briefly discusses the constitutional implications of the analysis.