The article discusses the findings of EU courts in the case concerning the German OPAL gas pipeline, which refer to the EU principle of solidarity. The implications of these findings have been examined. The author argues that the position of the courts in the entitled case goes beyond the issue of energy solidarity referred to in Article 194(1)(1) of the Treaty on the Functioning of the European Union and, in fact, concretizes the principle of sincere and genuine cooperation of Article 4(3) of the Treaty on European Union. He draws attention to the Court's wide-ranging obligation to take into account the interests and policies of all stakeholders in EU integration, which leads to a strengthening of EU integration, strengthens the position of the European Commission itself and may pose a problem in the judicial review of regulatory decisions.