The essay is made in response to a problem known for a very long time: ‘The laws that control people's lives must be understood and publicly known to them so that they can avoid what is prohibited and comply with what is permitted. And if something in these laws turns out to be unclear, it must be explained by the interpretation of the Emperor' (Code of Justinian, book I, tit. 14, item 9). It seems that the addressees of legal norms still often face difficulties in trying to correctly understand their content, in connection with which the presumption of knowledge of the law again forms the subject of academic discussion in an effort to give it a more refined meaning. It seems to be in a hurry to postulate knowledge of the correct understanding of the law for private individuals, all the more to impute such knowledge to them, if at least minimal guarantees have not been created for the opportunity to understand it correctly. According to the authors, the requirements of legal certainty, intriguing lawyers as guarantees of this kind, are hardly reducible in their potential to the unambiguity of the legal text alone. The relativism of the content of law, even in the most solemn (judicial) legal environment, is a characteristic that is not entirely accessible to correction. Understanding the law in judicial and other legal practice, albeit in different quantities, will always be changeable, and sometimes simply contradictory. At the same time, the meaningful ambiguity of the law, favorable to this, should not ipso facto lead to the disqualification of its individual norms and makes, rather, to consider guarantees of the legitimate interests of individuals, which compensate for the uncertainty of regulation. The authors have tried to ponder some types of such guarantees and propose to see their essence in protecting the legitimate expectations of individuals.