Law enforcement is decentralized. It is so despite documented interjurisdictional externalities which would justify its centralization. To explain this fact, we construct a political economy model of law enforcement. Under decentralization, law enforcement in each region is in accord with the preferences of regional citizens, but interjurisdictional externalities are neglected. Under centralization, law enforcement for all regions is chosen by a legislature of regional representatives which may take externalities into account. However, the majority rule applies for decisions made by the central legislature and this implies that the allocation of enforcement resources may be skewed in favour of those who belong to the required majority. We show that the choice between centralization and decentralization depends on the technology of law enforcement and the nature of the interjurisdictional externalities.