The Prohibition of Retroactive Effect in German and Hungarian Constitutional Law

Abstract

The aim of this study is to reconstruct the doctrine of the prohibition of retroactive effect and to conduct a comparative analysis of German and Hungarian constitutional court practice. The central question of the study is how the retrospective reassessment of legal situations that have already been concluded can be distinguished from future amendments to existing legal relationships, and what role legal certainty, the protection of legitimate expectations and proportionality play in this. The research employs normative, case-law-based and functional comparative methods; analysing landmark decisions of the German Federal Constitutional Court and the Hungarian Constitutional Court. The findings indicate that German law attaches different presumptions and burdens of proof to genuine and non-genuine retroactivity, whilst Hungarian practice applies the same substantive criteria within a less uniform conceptual framework. The study proposes a four-step test based on the sequence of historical connection, the finality of the legal situation, the disadvantage, protected reliance and provability. It concludes that the development of Hungarian legal doctrine requires not the mechanical adoption of German terminology, but rather a transparent and verifiable systematisation of the existing criteria for assessment.