The Chicago Gun Project (CGP) tests the effects of a neighborhood community and legal response to gun violence. Community organizations, neighborhood residents, and law enforcement officials developed an intervention with multiple efforts to induce normative changes within social networks of offenders regarding their participation in gun crime. The intervention seeks to reduce demand for guns and use of guns among young offenders by changing trajectories of legal social networks. The intervention also seeks to disrupt the spread of youth gun violence by focusing on the dynamics of social contagion that transmit violence within and across social networks of adolescents and young adults. The research is designed to test the effects of this intervention in two ways. First, we analyze patterns of gun crimes over time, using analytic models that apply methods of infectious disease epidemiology to identify the effects of the intervention. Second, we conducted surveys to show the links between perceptions of the response environment and individual decisions to engage in or desist from gun grime and crime generally.