EN
The first part of the article presents the legal basis for the principle of protection of acquired rights. The author indicates provision of consecutive constitutional acts from which it had been derived. He remarks that these provisions are very general in nature, and their normative content, as well as that of the principle of protection of acquired rights derived therefrom, is reconstructed by jurisprudence and literature in the course of application of law. The author systematises the views of the judicature and legal literature doctrine which tried to explain the way in which the norm demanding respect for acquired rights had been derived. He also presents his own approach when considering a relation between the principle of the state governed by the rule of law and the principles of protection of acquired rights. He gives the reasons why the principle of protection of acquired rights emanates from the principle of the state governed by the rule of law. The further part of the article deals with the nature of the principle of protection of acquired rights, its normative content. The principle is recognised in legal literature as both a general clause and a programme norm. The author criticises both approaches. The concept of rules and principles, developed by Dworkin and Alexy, with appropriate modifications and adjusted to Polish (positivist) system of law, seems to be more useful to describe the content of the principle of protection of acquired rights. Based on this concept, he argues that the principle of protection of acquired rights is an optimisation norm which requires the acquired rights be protected as fully as possible.