The role of European Union Courts in shaping the legal framework of accession to the European Union

The European Union’s enlargement of 2004 was a significant and symbolic event. From the legal perspective, it was also an event of a constitutional significance both for the European Union and for each of the ten acceding States. It was preceded by the complex legal process of harmonisation of laws, accession negotiations and the drafting and conclusion of the Treaty of Accession. The European Union enlargements have led to the development of dedicated case law of the European Union Courts with very characteristic features. In this respect the 2004 enlargement has given rise to a number of important judicial decisions that have contributed to the development of European Union law. The present article discusses the accession-related case law of European Union Courts classifying it along three categories. The first category concerns the ‘procedural’ case law covering the very process of accession and the legal status of the related legal instruments. Secondly, the ‘inter-temporal’ case law, that is the legal disputes related to the issues on the application of law in time are discussed. This category is particularly relevant in the context of accession, which entails, for the acceding State, the obligation to accept and immediately apply the entire body of European Union law, subject to any transitional measures agreed in the accession negotiations. Thirdly, the overview of the cases touching upon a broader, ‘constitutional’ perspective allows to complete the analysis by touching upon the axiology of the process of accession.