Who Litigates before the Court of Justice of the EU? Mapping Interest Group Participation in European Litigation

This paper addresses a gap in our understanding of strategic litigation in the European Union: who are the interest groups that choose to litigate before the Court of Justice of the EU (CJEU), and what factors shape their decision to pursue judicial strategies? While litigation has become an increasingly prominent tool in the repertoire of European interest groups, systematic analysis of participation, while existing, still remains limited compared to other fields of interest group studies. Building on the IGLitStrat Research project, this study maps the landscape of interest group litigation before the CJEU and explores the determinants of participation across policy sectors in between 2015 and 2024. The paper contributes theoretically by extending debates on legal mobilization beyond the well-studied US context to the unique institutional environment of the EU. Unlike American interest group litigation, EU strategic litigation operates within constraints including restrictive standing rules before the CJEU and variable access to national courts across member states. The paper examines three interconnected dimensions of interest group litigation. First, it identifies which type of organizations – business federations, professional associations, NGOs- engage more frequently in EU litigation and whether participation varies significantly across policy sectors. Second, it analyses the organisational characteristics that facilitate or constrain the choice to litigate, including financial resources, legal expertise, staff capacity, and mandate breath. Third, it investigates how external opportunity structures – such as legislative deadlock, ideological alignment with the Court, policy sector integration – influence strategic decisions to pursue litigation. This study draws on comprehensive data from judicial databases, including IUROPA and Eur-Lex, in conjunction with the EU Transparency Register, as well as targeted survey research. Doing so it examines why certain interest groups in specific sectors turn to courts while others with similar characteristics do not. By systematically coding organizational attributes, policy contexts, and temporal dynamics, the study identifies recurring patterns and outlier cases that illuminate the mechanisms driving participation decisions. Do decisions to litigate reflect calculations involving not only organizational capacity but also perceived judicial receptiveness, the availability of legal precedent or and the gap between EU and national law in specific policy areas? The findings have important bear particular relevance for understanding contemporary European governance. As legislative gridlock remains frequent and policy contestation intensifies, litigation represents an alternative route for interest group influence. However, if litigation access remains concentrated among well-resourced actors, this judicialization trend may exacerbate existing representation imbalances in EU policymaking. Understanding who litigates, and why, is therefore essential for assessing the democratic legitimacy and inclusiveness of legal mobilization as a mode of political participation in the European Union. This paper forms the foundation for broader analyses of litigation strategies and outcomes, providing the essential mapping required to understand how interest groups navigate the judicial arena in contemporary European politics.