NGOs’ strategic enforcement of EU environmental law: the case of ClientEarth

NGOs are increasingly becoming key actors in the implementation of EU law. Traditionally, they support the European Commission in its role as a centralized enforcer by filing complaints, which may lead to infringement proceedings. Since the early 2000s, however, we also increasingly see NGOs acting as ‘decentralized enforcers’ of EU law, bringing private litigation directly to national and European courts. This trend towards decentralized enforcement has been well-documented in the literature on implementation, where it has been attributed to a decrease in infringement proceedings brought by the Commission. From the NGO perspective, literature on litigation has also flourished, but often focuses on key strategic cases. We therefore know little about how NGOs in the EU decide between these two options: when and why do they support the centralized route – filing complaints to the Commission – and when do they take the decentralized route of litigation? In this paper, we bridge these two perspectives by systematically examining how one NGO – ClientEarth – acts on infringements within EU environmental policy. We trace ClientEarth’s activity from 2015-2025, mapping patterns in its use of complaints to the Commission and litigation across time. Interviews allow us to dig deeper into how the NGO makes strategic choices around enforcement of EU law. Analysing how these choices are made helps us to understand the extent to which NGOs can effectively push for the enforcement of EU law, and the implications for the coherence of enforcement across the EU.