Enforcing compliance with environmental regulations has been on the agenda for many years in many legal systems. The recent European Union directive concerning the protection of the environment through criminal law shows that criminal law is increasingly used as an enforcement instrument. However, recent theoretical Law and Economics literature, as well as scarce empirical literature tend to suggest that, given the high administrative costs of criminal law, administrative law could be the primary enforcement instrument under certain conditions. This paper contributes to this debate by providing some evidence on criminal enforcement decisions made by the environmental inspection agency, the public prosecutor and the judges for the environmental violations in the Flemish Region. The results suggest that legal systems which primarily rely on the use of criminal law to enforce environmental regulations, such as the Flemish Region, do not provide ex ante enough incentives for a violator to comply. This stems from the fact that the probability of being apprehended and prosecuted is relatively small, as well as the average fines imposed by the court. In addition to the low expected sanction a violator faces, more than 60% of cases are dismissed. Even though the reasons for this might be more nuanced, our results cast serious doubts on the effectiveness of criminal law enforcement of environmental regulations.