The present research investigates the normative roots of ingroup favoritism, reviving Tajfel's (1970) abandoned “generic norm” hypothesis according to which (1) most ingroups are perceived to promote ingroup favoritism and (2) people infer this normative prescription in newly assigned minimal groups. Anti-discrimination norms are also prevalent, but we propose that these originally emanate from external (and often supra-ordinate) entities that act as “moral referees” of the intergroup situation (e.g., the United Nations Organization). Two experimental studies using the self-presentation paradigm (Jellison & Green, 1981) supported these hypotheses in a naturalistic intergroup context (Study 1; N = 110) and in a minimal group paradigm (Study 2; N = 206). Moreover, the relationship between these norm perceptions and participants' tendency toward ingroup favoritism was examined. Results revealed differences in the naturalistic and the minimal group contexts. In the naturalistic setting, the relationship between perceived norms and people's actual tendencies was contingent on political orientation. In the minimal group paradigm, inferences of the ingroup norm were, overall, the best predictor of ingroup favoritism. These findings are discussed in the light of current models of intergroup behavior.