While historians have long studied the institutional dimensions of crime and punishment, this article examines the informal, extra-legal efforts of Nahuas and other residents of central Mexican communities to contend with violence and resolve conflicts. Residents of Nahua communities could not rely entirely on the authorities for protection and justice; rather, by being vigilant and taking matters into their own hands, they played a vital but underappreciated role in policing their communities, dealing with disorder, and preserving the peace. As such, they shouldered some of the law enforcement functions of the state apparatus. At times, their contributions could prove indispensable to the administration of justice. Their efforts not only helped to maintain public order and protect one another but they also tell us much about perceptions of acceptable behavior as well as notions of civic responsibility and, by extension, community membership and social solidarity.