Keywords: retroactivity, statute, non-retroactivity, primary and secondary retroactivity
Abstract: The article deals with the problems of applicability of laws with retroactive effects. Firstly, it deals with the acceptability of retroactive legislation as such. Secondly, it searches for rules governing the correct usage of laws that inflict existing legal relationships. The main problem is the possibility to use the laws in a retroactive way if the legislator did not expressly provide otherwise. Based on a historical and international comparison, the conclusion is that when the rules governing possible retroactivity of a statute are missing, the only way is to apply the law in a non-retroactive way.