University of Silesia in Katowice

English abstract: Referring to Józef Nowacki’s research on the principle of non-retroactivity of law [lex retro non agit], the authors of this study focus on the relationship between legal certainty and retroactive changes in the prevailing interpretation of legal provisions. The main topic of the study is the expression ‘interpretatio retro non agit‘, which is already well-known in the legal culture, but not widely used. The objectives of the study were: (1) to determine the content related, or potentially related, to the statement above in case law and literature; (2) to examine whether there are grounds to consider this principle as binding in adjudication; and (3) to explain why changes in the prevailing interpretation of legal provisions are perceived as a necessary evil. The research gave the authors a basis to distinguish between two understandings of the interpretatio retro non agit principle: the narrow one and the broad one. Moreover, the broad understanding contains four sub-types of the thus understood principle. The narrow approach prohibits recognizing a change in the prevailing interpretation as a circumstance that would allow legally valid court judgments or final administrative decisions to be challenged. On the other hand, the broad approach introduces a presumption that legal effects should not be ascribed solely because of a change in the prevailing interpretation that occurred after the legal fact took place. Four possible justifications for the interpretatio retro non agit principle were also considered: formal, natural, cultural, and instrumental justification. The authors found that the instrumental justification, which connects the principle with the value of legal certainty, seems to be the most appropriate. However, some elements of the principle can also be convincingly justified formally. Retroactive interpretation changes are only briefly discussed in literature, which the authors regard as an unfavourable state of affairs. However, the fundamental differences between law-making and the application of law allow us to understand that protecting the addressees of the law in practice is much more complicated in cases of applying the law.

Keywords: legal certainty, legal interpretation, consistent line of case law, interpretatio retro non agit, ex post facto laws

Language: Polish

Published: Number 3(36)/2023, s. 51-65.

DOI: https://doi.org/10.36280/AFPiFS.2023.3.51

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