On 1 May 2004, the EU experienced its largest single enlargement in terms of countries and people - with the accession of ten new Member States: Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovakia, and Slovenia.

To mark the 20th anniversary of the accession of these States, the CJEU hosted a conference on 2-3 May 2024 in celebration of this constitutional moment for Europe. The conference looked back on the history of the enlargement, the pre-accession context, and the criteria that candidate States had to meet. In a next segment, the conference participants analysed the contribution of the 2004 enlargement to the development of the EU as a "Union of values". The retrospective analysis also explored how, over the course of the past 20 years, EU law has ensured the cohesion and convergence of the national economies of the new Member States in the EU - under the supervision of the EU Courts.