The institution of citizen suits is a decentralized form of public participation that allows citizens to influence the implementation of public laws in courts. How does this institution influence policymaking? This article proposes a model of citizen suits. It then analyzes how this institution influences legislative decisions. The legislature bargains to choose the budget, distributive spending, and spending on an ideologically contested public good (e.g., health care or environmental protection). I find that citizen suits enable courts to forge a compromise between opponents and proponents of the public good by responding to the diverse claims of citizens. Anticipating the mobilization of citizens in courts, legislators in turn craft more socially efficient bills, with less distributive spending, which better represent the distribution of preferences for the public good compared to when citizens have no role in the implementation of legislation.