Social norms are vital for the functioning of adolescent peer groups; they can protect the well-being of groups and individual members, often by deterring harmful behaviors, such as aggression, through enforcement mechanisms like peer victimization; in adolescent peer groups, those who violate aggression norms are often subject to victimization. However, adolescents are nested within several levels of peer group contexts, ranging from small proximal groups, to larger distal groups, and social norms operate within each. This study assessed whether there are differences in the enforcement of aggression norms at different levels. Self-report and peer-nomination data were collected four times over the course of a school year from 1,454 early adolescents (M[subscript age] = 10.27; 53.9% boys) from Bogota, Colombia. Multilevel modeling provided support for social regulation of both physical aggression and relational aggression via peer victimization, as a function of gender, grade-level, proximal (friend) or distal (class) injunctive norms of aggression (perceptions of group-level attitudes), and descriptive norms of aggression. Overall, violation of proximal norms appears to be more powerfully enforced by adolescent peer groups. The findings are framed within an ecological systems theory of adolescent peer relationships.