This edited volume is a comprehensive and extensive analysis of key legal developments of the EU and its Member States during the two-decade period of the largest EU enlargement spanning 2004-2024, with insights on the EU's future. The accession of ten countries (Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia) was an unprecedented event in its scale and its long-lasting effects on security, stability and prosperity in Europe. Today's EU is the result of not only how Member States have benefitted from opportunities but also how they have responded to crises.

Part I emphasizes the EU as a peace-orientated integration through (the rule of) law. Part II reveals EU identity as a value-based legal entity and EU membership as a constitutional value among other aspects such as accession treaties and the experience of particular States (Latvia, Lithuania, Poland) with some historical discourse. Part III explores different aspects of European integration, such as principles of effectiveness and proportionality, issues of external relations, common foreign and security policy and the rule of law, jurisdiction of the EU Court of Justice and EU law-affected developments in national criminal law, civil law and procedure. Part IV addresses crucial issues pending for the Union in the nearest future, mainly further EU enlargement with a focus on Ukraine's accession (and the related issue of seeking justice) as well as the topics of the relation between EU law and national law and EU future reform.

The book is a source of knowledge and inspiration for researchers and practitioners in the field of EU law and should also be useful for anyone interested in EU law, EU membership, and EU law-affected fields of domestic law and further European integration.

Indre Isokaite-Valuze is an Associate Professor at the Law Faculty of Vilnius University in Lithuania.

Haroldas Šinkunas is a Professor at the Law Faculty of Vilnius University in Lithuania.