The link between external sanctions and intragroup normative control is examined to distinguish the conditions under which the two control systems augment or weaken one another. I construct a dynamic rational choice model that incorporates essential features of the sanction/norm link. The analysis suggests that much social control that appears to result from the sanctions of individuals derives instead from a form of group-mediated control termed compliance norms. In other contexts, intragroup control acts in opposition to external sanctions, resulting in aform of control termed opposition norms. According to the formal analysis, group responses to sanctions depend on the strength of sanctions, monitoring capacities, and the efficacy and cost of intragroup control.