Comment to Case C-391/17, Commission v. United Kingdom, Judgment of the Court of Justice (Grand Chamber) of 31 October 2019, EU:C:2019:919 and Case C-395/17, Commission v. The Netherlands, Judgment of the Court of Justice (Grand Chamber) of 31 October 2019, EU:C:2019:918 The judgments analysed both deal with the vicarious liability of Member States for their Overseas Countries and Territories (OCTs), an important issue of EU constitutional law.1 Both judgments also deal with the consequences of the duty of sincere cooperation for a loss of own resources to the EU budget due to acts or negligence of Member States. There are several technical complexities which make a rapid reading of the judgments, which differ somewhat in the two cases, more difficult. These complexities relate, first, to specific detailed issues on the application of the Overseas Association Decision of 1991 (1991 OCT Decision),2 and, second, to the liability of Member States for a breach of EU law towards the Union itself and towards other Member States. To sum up, the principle of vicarious liability of Member States for acts or negligence of their OCTs is clearly affirmed by the judgments in Commission v. United Kingdom and Commission v. The Netherlands. The Opinions of Advocate General Bobek provide further confirmation for that conclusion, even though he advised against accepting the specific claims of the Commission. The reasoning of the Court clearly shows that this vicarious liability is a consequence of the duty of sincere cooperation, as would have probably appeared even more clearly by endorsing the reasoning of Advocate General Cruz Villalon in his Opinion in Prunus, or the reasoning of this commentator, which is supported by the scholarship on EU overseas law.