The court that has jurisdiction over counterclaims under Article 6(3) of Regulation No 44/2001 also has jurisdiction over a counterclaim seeking reimbursement, on the ground of unjust enrichment, of a sum equal to the amount agreed in an extrajudicial settlement, where that counterclaim is brought in fresh proceedings between the same parties after the judgment in the original proceedings has been set aside, and the enforcement of that judgment gave rise to the settlement.

Where two actions against several defendants have different subject-matters and bases and are not linked by subordination or incompatibility, the mere fact that upholding one action could affect the extent of the right whose protection is sought by the other does not create a risk of irreconcilable judgments within the meaning of Article 6(1).

Article 6(2) covers a third-party action, brought under national law against the defendant in the original proceedings, for reimbursement of compensation that the third party paid to the applicant in those proceedings, where that action is closely linked to the original proceedings and was not brought solely to remove that defendant from the jurisdiction of the otherwise competent court.

The rule allowing several defendants to be sued in one court can apply to an action for damages and related disclosure brought jointly against undertakings that participated, at different times and in different places, in a single and continuous EU competition-law infringement found by the Commission. It still applies even if the claimant later withdraws its claim against the only co-defendant domiciled in the same State as the court seised, unless, when the proceedings were started, the claimant and that defendant colluded artificially to create or prolong the application of that rule.

In an action for damages for an infringement of Article 101 TFEU and Article 53 of the Agreement on the European Economic Area, jurisdiction clauses in supply contracts may be relied on even if they displace the jurisdiction rules in Article 5(3) or Article 6(1) of Regulation No 44/2001 - provided that those clauses refer to disputes about liability arising from an infringement of competition law.

There is a close connection, for the purposes of Article 6.1, between claims against several defendants domiciled in different Member States where, in circumstances such as those at issue in the main proceedings, they rely on rights to additional compensation that must be determined on a uniform basis.

Article 6.1 does not apply to defendants who are not domiciled in another Member State, even in proceedings against several defendants where some other defendants are domiciled in the European Union.

Where two or more companies established in different Member States are separately accused, in proceedings before a court of one of those Member States, of infringing the same national part of a European patent in force in another Member State by carrying out reserved actions for the same product, separate proceedings are capable of producing irreconcilable judgments under Article 6(1). It is for the referring court to assess whether that risk exists in the light of all the relevant information in the file.

Article 6(1) is not excluded merely because actions against several defendants for substantially identical copyright infringements are based on national legal grounds that differ between the Member States concerned. It is for the referring court to assess, in light of all the circumstances, whether separate proceedings would create a risk of irreconcilable judgments.

The special jurisdiction rule in Article 6, point 1, does not apply to disputes governed by Section 5 of Chapter II on individual contracts of employment.

Article 6(1) can apply even where the claims brought against several defendants have different legal bases.

Article 6(1) applies where, when the proceedings are instituted, the claims against different defendants are connected so that it is expedient to hear and determine them together in order to avoid the risk of irreconcilable judgments from separate proceedings. No separate inquiry is needed into whether the claims were brought with the sole object of ousting the jurisdiction of the courts of the Member State where one of the defendants is domiciled.

Article 6(1) may be relied on in an action brought in a Member State against a defendant domiciled there and a co-defendant domiciled in another Member State, even where national law treats the action as inadmissible from the moment it is brought against the first defendant.