This paper attempts to outline the virtues and the perverse effects of a Demerit Point System (DPS). Under a DPS, once overcome a given threshold of demerit points, infringers are punished by severe non-monetary sanctions (such as the temporarily suspension of driving license in traffic enforcement). Surprisingly, no comprehensive economic theory has been provided to support the widespread implementation of DPS. This paper tries to fill this gap. We show that the impact of a DPS depends on the distribution of preferences of the population of potential infringers. For some agents a DPS far from increasing deterrence may actually reinforce deviant behavior. Only for some group of agents, once a given threshold of accumulated penalties has been reached compliance may occur. Thus compliance is obtained only after some level of under-deterrence is tolerated. We then provide some policy suggestions in order to improve general deterrence under a DPS for any given level of detection policy. Our results seem to be consistent with available evidence.