This chapter offers an overview of the constituent elements of institutionalization in the European Union (EU), focusing on the processes of litigation and mobilization. The chapter is organized around four elements of these processes of institutionalization: the legal claim, litigation, legislative action and transnational mobilization. The legal claim gives rise to the litigation. The litigation activates European Court of Justice (ECJ) decision-making: a process that can lead to institutionalization to the extent to which the Court's judicial rulemaking expands the meaning and scope of EU law. This litigation in turn can alter legislative action at both the EU and national level. Finally, these institutional changes create the political opportunities for transnational mobilization: a process that once initiated can lead to institutionalization to the extent to which these transnational activists become increasingly formalized and expand the public sphere in EU politics.

The legal claim

As argued in Chapter 1, litigation is one process through which rule change can occur. In the EU, an increasing number of legal claims leading to litigation and ECJ decisions have dramatically influenced the shape of the Union. The Court's activism in the 1970s is now widely accepted as having transformed the Treaty of Rome, an international treaty governing nation-state economic cooperation, into a ‘supranational constitution’ granting rights to individual citizens (Lenaerts 1990; Mancini 1989; Stone Sweet and Brunell 1998a; Weiler 1981, 1991).