This paper analyzes the causes for regulatory compliance, using traditional deterrence variables and potential moral and social variables. We use self-reported data from 459 Tanzanian artisanal fishers in Lake Victoria. The results indicate that the decision to be either a non-violator or a violator, as well as the violation rate – if the latter – are influenced by changes in deterrence variables like the probability of detection and punishment and also by legitimacy and social variables. We also identify a small group of fishers who react neither to normative aspects nor to traditional deterrence variables but persistently violate the regulation.