The CJEU's Reasoning in Slovenia v Croatia: A Dispute Ancillary to Another Dispute, but Which One?

Slovenia brought a case against Croatia before the Court of Justice of the European Union (CJEU) on the basis of Article 259 TFEU alleging certain infringements of European Union law. Such infringements allegedly resulted from Croatia’s non-compliance with the Arbitral Award delivered by the Arbitral Tribunal established under the Arbitration Agreement concerning the land and maritime boundary between the two states. The CJEU decided that it lacked jurisdiction in this case. This article scrutinises the CJEU’s reasoning concerning its jurisdiction and argues that the dispute brought by Slovenia was ancillary to another dispute. Although the CJEU may have been right to decline to rule in this case, this article interrogates the legal reasoning on the basis of which the CJEU arrived at this conclusion. The core premise of the decision is that the Union is not a party to the Arbitral Agreement and the Agreement was therefore not binding on the Union. The focus on the Arbitral Agreement rather than Arbitral Award enabled the CJEU to avoid the elephant in the room: the question of whether the Arbitral Award was valid. This article demonstrates that in previous practice of the CJEU and other international courts and tribunals authoritative pronouncements on boundary disputes have constituted legal facts which were taken into account in subsequent judicial practice. In Slovenia v Croatia, the CJEU did not follow this practice and chose to focus on the treaty which constituted the tribunal. Although the CJEU may have been right to refuse to hear on the merits this ancillary dispute, the focus on the Arbitral Agreement rather than Arbitral Award was not persuasive.