Case law Developments in PIL

What Law Applies to the Issue of Res Judicata?

Should a foreign judgment entail in the requested State the res judicata effect that it has in the country of origin? Or should one rather substitute the foreign procedural effects of the judgment to fit with the law of the country where recognition is sought?

This issue was put to the test for the Court of Justice of the European Union (CJEU) in its judgment of 8 June 2023 in the French-English employment law matter BNP Paribas v. TR, C-567/21.

Claiming unfair dismissal, an employee first filed a lawsuit in England. After having been successful there, the employee claimed further compensation for the same dismissal in French courts. According to the CJEU’s judgment, the extent of res judicata under the Brussels I Regulation shall follow the country of origin of the judgment. However, not all national procedural rules can be characterised as res judicata rules with international effect. Only rules concerning the ‘authority and effectiveness’ can have international res judicata effect according to the CJEU’s judgment.

In previous posts for this blog, Fabienne Jault-Seseke has reported on the questions referred to by the CJEU and criticised the opinion of Advocate General Priit Pikamäe. François Mailhé has also written in this blog about a parallel French Cour de Cassation case where questions regarding res judicata were referred to the CJEU. That case (Recamier v. BR, C-707/21) is still pending before the CJEU. As the discussion of res judicata in EU private international law can easily be deepened, the following post will focus on the judgment of the CJEU in the BNP Paribas case only.


In 1998, the French bank BNP Paribas hired an employee to work for the bank in London. That employment contract was governed by English law. In 2009, the parties entered a new employment contract to regulate the secondment of the employee to Singapore. The new employment contract was governed by French law. After a little more than a year in Singapore, the employee was relocated back to London. The relocation was regulated with an amendment to the French employment contract.

A few years after the return to London, the employee was dismissed for serious misconduct that had taken place during his secondment to Singapore. The dismissal was challenged by the employee, who brought an action in an English court claiming compensation for unfair dismissal. In its judgment, the English court held that the claim was well founded. In the English judgment, it was clear that the employer had taken disciplinary measures based on French law. Under English law, which was agreed to be applied by the parties in the case, those measures were unlawful. Consequently, the bank was ordered to pay a compensatory award of GBP 81,175.

Two months after the English judgment was delivered, the employee initiated new legal proceedings against the bank demanding additional compensation for the same dismissal that the English court had based its judgment on. The new lawsuit was filed in a French labour court. With reference to res judicata due to the English judgment, the French labour court held that the claims were inadmissible. This decision was appealed and the French court of appeal came to a different conclusion. Holding that the claim settled by the English court was limited in scope, the French court of appeal stated that the claims made in France were not precluded on the grounds of res judicata. Even if res judicata generally means that a legally settled matter is precluded and cannot be litigated again, there are different understandings of the concept in different jurisdictions. As the case was brought to the French Supreme Court (Cour de Cassation), the private international law issue of the law applicable to res judicata was referred to the CJEU for a preliminary ruling.


First, the CJEU held that the old 2001 Brussels I Regulation (44/2001) was applicable in the case, as the English judgment was given in a legal proceeding instituted before 10 January 2015. According to the transitional provisions in article 66(2) of the Brussels I bis Regulation (1215/2012), it is that date that is decisive in the application of the two regulations.

As regards judgments delivered in other member states, the main principle of the Brussels I Regulation is that such judgments shall be recognised and enforced in all other member states. However, as the CJEU noted in its judgment, the notion of ‘recognition’ is not defined in the regulation. Recognition of judgments in the EU rests on the principle of mutual trust. Therefore, a judgment from another member state may not be reviewed in substance. With reference to this line of purposive and systematic argumentation, as well as to the fact that the explanatory report from 1979 (the Jenard report) explicitly stated that judgments shall have the ‘authority and effectiveness accorded to them in the State in which they were given’, the CJEU held that it is the law in the country of origin of the judgment that determines the extent of res judicata.

Even if it is the law in the country of origin of the judgment that determines the extent of res judicata, the CJEU noted in its judgment that national procedural rules must be classified (characterised) as res judicata rules for this choice of law rule to be applicable. In the case at hand, the issue was whether an English procedural rule that required the parties to centralise all their claims relating to the same legal relationship to a single procedure was a res judicata rule with an inadmissibility effect for the subsequent French procedure. In its judgment, the CJEU stated that one must – as a legal test of whether a national procedural rule is a res judicata rule – assess whether the national procedural rule ‘concerns the authority and effectiveness’ of the judgment (para. 49). Using this legal test, the CJEU held that the English rule on centralisation of claims served the interest of sound administration of justice rather than being intended to govern the authority and effectiveness of a judgment. Therefore, the English rule was not considered to be a res judicata rule that should have any inadmissibility effect for the subsequent French procedure.


By its judgment, the CJEU has confirmed that res judicata follows the law of the country where the judgment was delivered. This is the same principle as delivered already in Hoffman, 145/86. It is not the choice of law rule that is new in the BNP Paribas case, but the characterisation methodology that the CJEU seems to embrace. What is special to characterisation in private international law is that the issue itself contains a choice of law problem.

Traditionally, a legal notion should either follow the law where the issue arose (lex causae) or the law of the forum (lex fori). In setting an autonomous legal test for what national procedural rules can be characterised as res judicata rules, the CJEU has chosen a lex fori approach to the issue of characterisation for determining what aspects of res judicata that follow from the country of origin. Ultimately, this approach will improve foreseeability and harmonisation.

However, until the framework of the notion is known, it may be hard to assess what really is a national procedural rule that has international res judicata effect. Perhaps further guidance will be given already in the forthcoming Recamier case mentioned above.

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