Principles of Interest Group Organization in the Czech Republic: Legal Rules and their Changes as a Result of Europeanization This paper seeks to find out to what extent the process of EU accession has influenced legal regulations concerning the creation and functioning of social and political actors. Through the analysis of various statutes and changes made to them, the paper tries to determine the role the EU plays in amending assembly legislation. The actors under scrutiny include political parties, professional organizations, labour unions, and civil society organizations. The paper concludes that the most influenced field of actors was the area of chambers of professionals which was obliged to conform to requirements for the free movement of people and services in the European Union in order to comply with European law. The Czech Republic was quite leisurely in their harmonization of statutes, with the majority of them passed just before accession to the EU. An interesting part of the problem concerns the question of political party membership, which is still reserved only for Czech citizens. However, European citizenship, with its voting rights to the European Parliament and local magistrates, is arguably going to push slowly for change even in this domain.