The main purpose of this paper is the identification of criteria that justify the choice of (costly) criminal law enforcement over administrative or tort law to address harmful activities. Specifically, using a Law and Economics approach, this paper demonstrates when and why criminal law should be used and what the comparative advantages of criminal law are over other legal alternatives. By not exclusively focusing on the distinction between tort and crime, but also on the use of criminal law vis-a-vis administrative law, this paper will provide some contributing remarks to existing literature. Based on the analysis in this paper, it is argued that criminalization of an act should occur in areas where: (1) harm (or benefit to the criminal) is large and/or immaterial and/or diffuse and/or remote; (2) prosecution of a violation creates stigma; (3) the probability of detection is low; and/or (4) criminalization carries an educative role. Under these circumstances, ceteris paribus, criminal law is justified as the most efficient instrument to internalize the social cost of harms.