Variance in Civil Society Organisations’ Litigation Strategies in the EU: Internal and External Constraints and Opportunity Structures

Over the past two decades, civil society organisations (CSOs) have increasingly turned to strategic litigation to shape European Union policies. Yet significant variation exists in their reliance on courts across policy domains. This article investigates why CSOs in some sectors litigate more frequently than others, focusing on asylum and migration, environmental protection, and data protection between 2010 and 2025. Drawing on a newly assembled dataset that combines CJEU case law, the EU Transparency Register, and CSO-specific information, we systematically compare litigation strategies across the three fields. The results reveal significant differences: CSOs in environmental protection are the most active litigants, those in asylum and migration the least, with data protection actors situated in between. We argue that this variation can be explained by the interplay of internal opportunity structures - notably financial and human resources - and external opportunity structures, including the openness of judicial and political venues. Together, these factors condition CSOs’ capacities and willingness to pursue legal strategies as part of their broader advocacy toolkit. By developing a cross-sectoral analytical framework the article contributes to theories of interest representation in the EU. It demonstrates that litigation is not only resource-dependent but also context-dependent, offering new insights into the multilevel opportunity structures shaping CSOs’ strategic choices. The article provides new evidence on how civil society actors engage with the EU legal system. It thus sheds light on the broader patterns of integration through law and the differentiated strategies of European interest representation.