This article addresses the principle of res judicata in the context of rules on State aid, including the case-law of the Court of Justice and the 2021 Commission Notice on the enforcement of State aid rules by national courts. The limits of the principle at issue required by Article 108(3) TFEU and the powers of national courts to recover unlawful aid (with or without a recovery decision from the Commission) are discussed. The law is stated as it stood on 1 January 2022 (with some later developments). The case-law on res judicata referred to here includes the decisions of the Court in Lucchini, Klausner Holz, and CSTP/Buonotourist, with commentary on the practical effect of the Court’s approach.
Keywords: Lucchini; Klausner Holz; res judicata; Article 108(3) TFEU; national courts