During the last 20 years, the European Union has been mired in crisis after crisis. At the same time, the number of infringement procedures, the formal requests from the European Commission to member states for compliance, decreased dramatically, despite the addition of 10 member states in 2004. Yet, the link between crises and Commission enforcement activity has not been systematically examined.

In this article, I theorize about the role of time, and demonstrate that crises limit the Commission's ability to act as guardian of the treaties. However, crises are not deterministic in nature – the European Parliament and European Union citizens can alter the costs of Commission enforcement.

I find that as Euroscepticism increases, the Commission's demand for compliance decreases, in part due to the steep reputational costs to the Commission when member states refuse compliance, especially after sanctions. The number of infringements is also positively correlated with European Parliament action, suggesting that even without formal sanctioning power, the European Parliament plays a role in European Union law enforcement.