Drawing on a decade of research, this article demonstrates that the California Correctional Peace Officers Association (CCPOA), the labor union that represents prison officers in the Golden State, became one of the nation's most successful and politically influential unions in the 1990s due to a combination of social and penal developments, and the organization's politically realistic model of unionization. To advance its members' interests and a particularly punitive vision of the public good, the CCPOA implemented tactics typically associated with social movement unionism, such as forming and working with nonlabor community groups (in this case, crime victims' organizations). Showing that the CCPOA was (and, in some ways, still is) a key participant in the conservative movement for “law and order,” this article extends our understanding of social movement unionism. It also argues that scholars, activists, and organizations committed to labor unions and progressive penal reform must struggle with groups like the CCPOA to move forward a conception of the public good based on justice, equality, and fairness.