The Regulation (EU) 2023/2405 of the European Parliament and of the Council of 18 October 2023 on ensuring a level playing field for sustainable air transport (ReFuelEU Aviation) can be found in all the official EU languages using the following link:
https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32023R2405
See also:
https://transport.ec.europa.eu/transport-modes/air/environment/refueleu-aviation_en