The European Union must finance the repayment of the debt it has contracted through Next Generation EU (NGEU). This has brought a new dynamic to the debate on the reform of its financial order. The ideas put forward in this context are diverse and sometimes unorthodox, thereby provoking questions on the legal limits set by the existing Treaty framework. The article complements this debate by focusing on the specific instrument that determines the resources available to the EU – the Own Resources Decision (ORD) pursuant to Article 311(3) TFEU. It seeks to answer one question: What is the correct legal framework the European Court of Justice (ECJ) would have to apply in a case in which it is asked to rule on the legality or validity of the ORD? To explore this question, it analyses the legal requirements contained in Article 311(3) TFEU, discusses the legal nature of the ORD, and examines what type of review the ECJ would be able to exercise regarding its different procedural and substantive aspects.