SignificanceIn a social dilemma, total resources are maximized if everyone cooperates, but everyone is tempted to not cooperate. Cooperation may be impossible if the parties interact infrequently or do not have sufficient information about each other’s past behavior. In such cases, human cooperation is often maintained by third parties who specialize in enforcement (e.g., a police force). However, if enforcers are powerful enough to punish noncooperators, they may also be powerful enough to extract resources from their clients without providing any services in return. We show that by using a reputation system, enforcers can police each other and sanction those who fail to punish noncooperation in the social dilemma.