101 Anna Dalkowska 1 Przemysław Ostojski 2 Selected problems of changes in EU and natonal legislaton in the perspectve of the principles of legitmate expectatons and legal certainty DOI: 10.5604/01.3001.0013.9037 Summary This article addresses selected problems related to the complex topic of changes in EU and national legislation. The considerations contained in the article focus on the so-called pre- vious effectiveness of an EU directive and on the retroactivity of (ordinary) laws passed by EU Member States. The research perspective concentrates on the functioning of these institutions in the face of the principles of legitimate expectations and legal certainty. The article utilizes primarily and predominantly the analytical method, as well as the empirical method, making use of the extensive case law of the EU Court of Justice and the Supreme Administrative Court. As a result of the research, it shall be stated that, frst and foremost, the source of legitimate expectations of an individual cannot be an EU directive during the transposition there of in an EU Member State. Secondly, the principle of legal certainty is not precluded by the exceptional retroactive effect of a normative act, due to the need to protect the public interest, provided that legitimate expectations of individuals are guaranteed. Keywords: the principle of legitimate expectations, the principle of legal certainty, change of law, retroactivity of law, directive I Introductory remarks The issue of changes in EU or national law is closely related to the con- vergence of public administration in the Member States of the European Union. The phenomenon of not only harmonization, but also unification of legal and administrative solutions – both in the legal and organizational space of the European Union, as well as in the Member States – is implemented mainly through changes in law. Due to the jurisprudence of the Court of Justice of the European Union, which applies EU law, legal and administrative standards are converging, including through uniform legal principles in the Member States. Among these principles, the most signifcant are the principles of legal certainty and protection of legitimate expectations, referring mainly to the broadly under- stood subject of intermittent law. 1 Phd,Dr.ofLawattheWSBUniversityinGdańsk,judge,UndersecretaryofStateintheMinistryofJustice,Editor-in-Chief of „Nieruchomości@”, Member of the Academy of European Law Governing Board, ORCID: 0000-0002-8815-3006; 2 PhD, Dr. of Law, professor at the School of Management and Banking, in Poznań, Prosecutor at the District Public Prosecutor’s Offce in Poznań delegated, to the National Public Prosecutor’s Offce, ORCID: 0000-0001-6552-8162