A claim for reimbursement brought in connection with the rehearing of an original action as a result of the setting aside of the judgment delivered in that action, which had become final, must be classified as ‘legal proceedings’ within the meaning of Article 66(1) of Regulation No 44/2001 on jurisdiction and the recognition and enforcement of judgments in civil and commercial matters. While the domestic laws of the Member States may differ as to how the principle of res judicata is implemented, the fact that under the relevant national procedural rules such a judgment has become final suffices for it to be considered that a subsequent application to a court on the basis of unjust enrichment of the other party falls within the concept of ‘legal proceedings’ within the meaning of that provision.

As regards the application ratione temporis of Regulation No 44/2001 on jurisdiction and the recognition and enforcement of judgments in civil and commercial matters, where all the questions asked in a request for a preliminary ruling concern legal proceedings for unjust enrichment brought by the applicant in 2008, those proceedings fall within the temporal scope of that regulation.

Article 6(3) of Regulation No 44/2001 on jurisdiction and the recognition and enforcement of judgments in civil and commercial matters must be interpreted as meaning that the court designated by that provision as regards counterclaims has jurisdiction to hear a counterclaim seeking the reimbursement on the ground of unjust enrichment of a sum corresponding to the amount agreed in an extrajudicial settlement, where that claim is brought in fresh legal proceedings between the same parties, following the setting aside of the judgment delivered in the original proceedings between them, the enforcement of which gave rise to the extrajudicial settlement.

First, the counterclaim must be separable from the claimant’s action and seek a separate judgment. Thus, in circumstances in which a lessee under a leasing contract brings a counterclaim against the lessor following the setting aside of a judgment ordering the lessee to pay a sum equivalent to the instalments due under the leasing contract together with contractual interest, the claim for reimbursement of the payment made in enforcement of the extrajudicial settlement constitutes a separate claim by the lessee seeking for a separate judgment to be given against the lessor to repay what was wrongly paid to him.

Secondly, Article 6(3) of Regulation No 44/2001 requires the counterclaim to arise from the contract or facts on which the original claim was based, an expression which must be given an autonomous interpretation, having regard to the objectives of that regulation. It is in the interests of the sound administration of justice that the special jurisdiction for counterclaims enables the parties, in the same proceedings and before the same court, to litigate all their claims against each other that have a common origin. The counterclaim for reimbursement on the ground of unjust enrichment must be regarded as arising from the leasing contract from which the lessor’s original action originated, where the alleged enrichment in the amount of the sum paid in enforcement of the judgment that was subsequently set aside would not have taken place without that contract.

(see paras 32-40, operative part)