Considered an unusually powerful actor that has furthered European integration, the Court of Justice of the European Union (CJEU) has attracted considerable interest from both scholars and the public. Legal scholars and political scientists, as well as historians, have studied the Court in the context of it being one of the main actors in the integration process. Those that saw European integration as “integration through law” originally considered the Court to be the core element driving this process. The Court’s case law has influenced market integration, the balance of power among the EU’s institutions, and the “constitutional” boundaries between supranational and national competences. The pathbreaking rulings Costa vs. Enel and van Gend en Loos introduced new legal principles of direct effect and primacy in the 1960s; the 2007 Laval and Viking rulings triggered criticism of the Court’s decision, which was said to put the rights of companies above those of workers; whereas the Mangold ruling in 2005 on age discrimination was widely welcomed in spite of some negative reactions in Germany.
Hence, while “integration through law” remains a powerful narrative in the academic field of European studies, the Court’s decisions and its role in the EU system have not remained unchallenged. This view of the Court as being less central to European integration is based on two developments in this field of study. On the one hand, research findings based on various analytical approaches—from rational choice to post-positivist—suggest that “integration through law” since the beginning of European integration has been a far less straightforward process than we have otherwise been led to believe. Scholars assert that the Court has been constrained by political, administrative, and constitutional counteractions since its establishment in 1952. On the other hand, scholars have identified a number of developments in the integration process from the early 1990s and the Maastricht Treaty, such as the increase in new modes of governance and intergovernmental decision-making, that explain why the Court’s role has come into question. Understanding these debates is crucial to grasping the broader institutional as well as political and legal developments of European integration.