Supremacy or Primacy of EU Law—(Why) Does it Matter? Matej Avbelj* Abstract: Even 50 years on the principle of supremacy or primacy is still surrounded with ambiguity, which is apparent already on the level of semantics. The principle has not carried a single name, but three. This paper argues that a disparity in the denomination of the principle amounts to much more than semantics. It exhibits conceptual differences. Different conceptualisations of the principle of primacy or supremacy entail different models of structural principles of EU law: the hierarchical, the conditionally hierarchical and the heterarchical model. These are no mere theoretical constructions; rather they have influenced concrete practices of EU law, including the most recent Kücükdeveci case as well as the Lisbon decision of the German Constitutional Court. While none of the three models has yet found an unequivocal and conclusive endorsement in the EU practice, there are compelling theoretical and practical reasons for which one of them should be preferred over the others. Whether EU law has supremacy or primacy therefore matters. I Between Semantics and Conceptual Differences It has been almost five decades now since the European Court of Justice (ECJ) laid down the so-called principle of supremacy of EU law. However, even after all this time the principle continues to be surrounded with a considerable degree of ambiguity. This is visible already on the level of semantics. The principle has carried not a single name, but three. Not a small number of legal commentators have consistently addressed it as supremacy; the majority has referred to it as supremacy or primacy, using both labels interchangeably; while the minority of scholars has stuck to the language of primacy. This disparity in the denomination of a fundamental principle of EU law would be of little interest, was it not so strongly entrenched and simultaneously so much at odds with the actual jurisprudence of the ECJ. There have been only two judgments in which the ECJ has employed the language of supremacy: the Walt Wilhelm 1 and the Fratelli * Assistant Professor of European Law, Graduate School of Government and European Studies, Kranj, Slovenia. 1 Case 14/68, Wilhelm v Bundeskartellamt [1969] ECR 1, para 5: ‘in conferring on a Community institution the power to determine the relationship between national laws and the Community rules on competition, confirms the supremacy of Community law’. The term ‘supremacy of Community rules’ can be found among the keywords as well. The term ‘supremacy’ also appears among the keywords in the Case 93/71, Leonesio v Ministero Dell’Agricultura e Foreste [1972] ECR 287, but not in its text. European Law Journal, Vol. 17, No. 6, November 2011, pp. 744–763. © 2011 Blackwell Publishing Ltd., 9600 Garsington Road, Oxford, OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA