Why should criminal law be used to enforce environmental violations? Aren"t administrative sanctions, particularly administrative fines, more efficient to use? From an economic perspective, this book examines the question as to why society should enforce certain violations through criminal law, while others through private or administrative law. The findings of this analysis show that the enforcement through criminal law should be used only in limited circumstances - i.e. when (1) harm is large and/or immaterial and/or diffuse and/or remote; (2) stigma is desired; (3) the probability of detection is low; and (4) the criminal enforcement costs are sufficiently low. Under these circumstances, criminal enforcement seems to be the efficient instrument to use. This framework was applied to the enforcement of environmental violations in the UK, the Netherlands, Germany, and the Flemish Region in Belgium. The empirical assessment of these four jurisdictions shows that there is definitely a role for administrative sanctions, which could be a cost-effective instrument to deal with environmental violations. The relevant factors in assessing whether administrative fines are welfare enhancing are the distribution of abatement costs among firms, the marginal enforcement costs, and the probability of detection and sanctioning. The analysis shows that - in order to benefit from having two separate systems of laws, namely the criminal and the administrative - procedural differences should be maintained, since they have an economic justification. (Series: European Studies in Law and Economics - Vol. 8)