ABSTRACT – This paper examines the conditions under which the lex mitior principle, enshrined in the final sentence of Article 49(1) of the Charter, applies in light of the criteria laid down by the Court of Justice in the BAJI Trans judgement (C-544/23). In particular, it focuses on four key issues: the scope of application of the Charter; the criminal nature of the offence; the types of legislative amendments that trigger the application of the principle; and, lastly, the absence of a final decision. Particular attention is paid to the development of both the autonomous European notion of “criminal matter”, which entails the application of the lex mitior principle to punitive administrative sanctions, and of the concept of a “final decision”, as the temporary boundary beyond which the principle can no longer operate. The final part addresses some questions left unresolved by the judgement, focusing in particular on whether the application of the criteria it establishes may, in certain circumstances, result in conflicts with national rules.
