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Best practice for handling foreign law

The Hamburg Guidelines support German courts, experts, and parties in handling foreign law in international disputes – what they say and how to use them.

Peter Poleacov6 min

Best practice for handling foreign law

Background

In a dispute, a German court also has to decide questions of foreign law to the extent foreign law applies. This duty flows from Section 293 ZPO: the court is not limited to the evidence the parties bring, but is also authorized to draw on other sources and to order what is necessary to that end.

The court must determine foreign law of its own motion. How it obtains the relevant knowledge is in its sound discretion. Free-form evidence (Freibeweis) applies: the court may use any means of evidence and any source of knowledge. The court’s options include commissioning an expert opinion on foreign law. The expert’s role, however, is limited to answering the court’s evidentiary questions about foreign law. The determination, interpretation, and application of the private international law (PIL) in force in Germany, and the decision of the specific case (fact-finding and application of foreign law to those facts) remain the court’s own task.

That expert opinion, however, is not the standard route but the last resort. The Hamburg Guidelines say so expressly: in view of the cost and delay an expert opinion generally entails, it should be commissioned only where the relevant foreign law cannot be determined with sufficient certainty by simpler, faster, and less expensive means.1 That matches the BGH’s line, under which an expert opinion is unnecessary where the foreign provision is clear and no in-depth engagement with foreign case law appears necessary.2 For you as a party, that is the most practical sentence in this article: if you want to avoid an expert opinion, hand the court the simpler routes before it has to look for them itself.

Where the decision turns on foreign law, the court must discuss this with the parties (right to be heard) and give them an opportunity to address its determination and content. Where the court has formed a preliminary view of the content of foreign law, for example based on its own research, it shares that view with the parties (Hamburg Guidelines (2023), Art. 2 § 2 No. 2).

The parties to the dispute may help the court determine foreign law, but they are generally not obliged to do so beyond their general duty to promote the proceedings and to cooperate. Foreign legal rules are treated as rules of law, not as facts, so the principles of burden of pleading and proof do not apply.3 For tactical reasons each party should nonetheless make submissions on foreign law. That alone makes it worth being represented in an international dispute by experienced, specialized counsel who can run the case confidently and persuade the court.

Under the BGH’s settled case law, the competent court must determine and apply foreign law in the way it is, or would be, applied by the courts of the respective country.4

How far the duty to determine foreign law reaches cannot be stated in the abstract. In 2025 the BGH again stressed that the limits of the trial court’s discretion are set by the circumstances of the individual case, and that the requirements rise the more complex or unfamiliar the applicable law is compared with domestic law. Simply consulting the sources is not enough: the German judge has to apply foreign law as the judge of that country interprets it, taking account of the legal practice there, in particular its case law.5

In interim relief proceedings a milder standard applies. There, instead of a determination under the general principles of Section 293 ZPO, prima facie evidence under Section 920(2) ZPO in the sense of a summary plausibility review should suffice, weighing the interests of both sides.6

The application of foreign law itself is, according to the BGH, not reviewable on revision (referring to Section 560 ZPO in conjunction with Section 545 ZPO). The revision court is in principle bound by the findings of the court of appeal on the content of foreign law. In other words: German law is reviewable on revision; foreign law is not. The determination of foreign law, however, is subject to review by the highest court.7

The Hamburg Guidelines

The “Hamburg Guidelines on the Determination and Application of Foreign Law in German Proceedings” (Hamburg Guidelines), developed through close exchange between practice and academia and published by the Max Planck Institute for Comparative and International Private Law in Hamburg, support courts, experts, and parties (including their representatives) in handling foreign law in international disputes. They set out the relevant legal framework in compact form and offer a range of practical recommendations (Michaels/Schmidt, Die Hamburger Leitlinien zur Ermittlung und Anwendung ausländischen Rechts in deutschen Verfahren, NJW 2024, 24, with further background, content overview, and outlook).

The Hamburg Guidelines are primarily aimed at proceedings before civil courts, but apply in principle to other cases as well where German courts or authorities (for example, tax courts, criminal courts, asylum authorities, tax offices, civil registry offices) have to apply foreign law (Hamburg Guidelines (2023), preliminary remarks).

The Hamburg Guidelines do not address the international jurisdiction of German courts, because courts can and must answer that question independently on the basis of the relevant legal sources (for example, Brussels Ia Regulation, Brussels IIb Regulation, Sections 97 et seq. FamFG) (Hamburg Guidelines (2023), preliminary remarks).

Summary

The Hamburg Guidelines are a useful instrument, but they do not change the underlying arithmetic. Foreign law before a German court costs time and money, and the outcome depends on how well the court penetrates an unfamiliar legal system. What the Guidelines achieve is to order that process: they push the expensive expert opinion into the role of a last resort and hand the parties the means to avoid it.

The real consequence, though, lies earlier, in the contract. A party that aligns governing law and jurisdiction never ends up in this situation. How differently the new Commercial Courts handle this is covered in the article “Commercial Courts in Germany” – in Saxony, for instance, jurisdiction is confined to disputes governed by German law.

The Hamburg Guidelines are licensed under the Creative Commons License CC-BY 4.0. Published by the Max Planck Institute for Comparative and International Private Law, Hamburg. Authors: Prof. Dr Ralf Michaels and Priv.-Doz. Dr Jan Peter Schmidt. The Hamburg Guidelines are available here.

Notes

  1. Hamburg Guidelines (2023), Art. 2 § 3 No. 5, as reported by Dostal, Die Ermittlung und Anwendung ausländischen Rechts gemäß § 293 ZPO im Licht der jüngsten Rechtsprechung des Bundesgerichtshofes, IWRZ 2025, 287. ↩

  2. BGH, order of 30 March 2021 – XI ZB 3/18: an expert opinion was unnecessary because no contested questions of interpretation arose that would have required in-depth engagement with English case law, and the sources were readily accessible. ↩

  3. Hamburg Guidelines (2023), Art. 1 § 1 No. 3 referring to BGH, order of 24 August 2022 – XII ZB 268/19. ↩

  4. see BGH, judgment of 5 July 2023 – IV ZR 375/21 marginal no. 27. ↩

  5. BGH, order of 20 February 2025 – I ZB 26/24. ↩

  6. Dostal, IWRZ 2025, 287, on the reduced standard of review in proceedings under Sections 916 et seq. and 935 et seq. ZPO. ↩

  7. see BGH, judgment of 5 July 2023 – IV ZR 375/21 marginal no. 24. ↩

Reference: Poleacov, P. (2026). Best practice for handling foreign law. INN.LAW. https://inn.law/en/perspectives/hamburg-guidelines/