Route 66: Mutations of the internal market explored through the prism of citation networks.

The article analyzes the transformation of the European Union's internal market from a free trade area focused on liberalization—the removal of unlawful national barriers to free movement—to a complex regulatory system emphasizing harmonization through common policies and legislation. Using community detection techniques on the European Court of Justice's case law, it identifies a decisive shift between 2007 and 2010, marked by increased litigation related to legislation in diverse policy areas beyond purely economic concerns, such as social policy, environment, and security. This two-dimensional mutation reflects a change in the rationale of integration from state-centered, economic liberalization to EU-centered, policy-driven harmonization, raising important questions about the EU's authority and justification to regulate in domains traditionally reserved for member states. The study offers a novel empirical framework linking legal methods of integration to their underlying political and economic rationales, contributing to ongoing debates on competence, legitimacy, and the future direction of European integration.