Political Influence and Judicial Authority in the EU: How Member States and Advocates General Shape CJEU Decision-Making

The preliminary ruling mechanism is one of the central channels through which the Court of Justice of the European Union (CJEU) interacts with national judiciaries, and a key instrument structuring judicial authority in the EU’s multi-level governance system. By enabling domestic judges to refer questions on EU law, the procedure not only fosters the uniform interpretation of EU rules but also alters the balance of power between national courts, national executives, and supranational judicial actors. Understanding who influences the CJEU’s decisions in this process is therefore essential for assessing the Court’s independence and its role as a political actor in European integration. This paper examines the strategic interplay between Member States’ written observations and the opinions of Advocates General in shaping the outcomes of preliminary rulings. It investigates whether, and under what conditions, the CJEU aligns with state preferences or instead relies on the epistemic authority of the Advocate General—focusing in particular on whether this dynamic varies with the institutional position of the referring court within the domestic judiciary. Drawing on the Iuropa Project dataset covering 5,333 referred questions and 41,712 written observations, we find that when the Advocate General and at least one Member State converge, the CJEU very rarely deviates from that position. When they diverge, however, the Court systematically tends to follow the Advocate General, suggesting that technocratic expertise may outweigh intergovernmental pressure. These patterns offer new insights into supranational judicial independence, the formation of a “European judicial power,” and the evolving configuration of authority within the EU’s constitutional architecture.