On 17 September 2026 the Unified Patent Court Court of Appeal held that national procedural law determines whether a prior national judgment bars a subsequent validity challenge in the same jurisdiction. The ruling interprets Article 113(1) of the Agreement on a Unified Patent Court to give each participating Member State the authority to apply its own res judicata rules to UPC proceedings. Patent owners and alleged infringers in Germany now face a clearer split between national and UPC litigation, limiting the ability to relitigate validity after a German court decision.

Full News Breakdown

The dispute arose from parallel infringement proceedings in a German regional court and a UPC division concerning the same European patent. The German court had already decided on the patent’s validity, and the UPC division was asked to revisit that issue. The appellate panel concluded that the German procedural framework precludes a second validity assessment in the UPC for the same patent.

• Case Name: UPC Court of Appeal, German validity‑challenge case

• Court: Unified Patent Court, Court of Appeal

• Panel: Three‑judge panel (names omitted)

• Date: 17 September 2026

• Citation: UPC CA 2026/09/17

• EU Instruments / UK Legislation Cited: Agreement on a Unified Patent Court; Regulation (EU) No 1257/2012 (unitary patent); Implementing Regulation (EU) No 540/2012; German Patent Act (PatG)

• Key Provisions: Art. 113(1) UPC Agreement; Art. 115(1) UPC Agreement; Art. 9 PatG (res judicata)

• Primary Legal Issue: Whether national res judicata rules apply to UPC validity challenges after a national judgment on the same patent

• Applicant/Plaintiff Arguments: The patent holder argued that the UPC’s exclusive competence under Art. 115(1) overrides national res judicata, allowing a fresh validity review.

• Respondent/Defendant Arguments: The alleged infringer contended that the German court’s decision should be binding on the UPC division under national procedural law.

• Court's Reasoning: The panel held that Art. 113(1) expressly preserves the competence of national courts to apply their own procedural bars, and that Art. 115(1) does not abrogate those rules.

• Holding: National procedural law governs the admissibility of repeat validity challenges in the UPC.

• Operative Order: The UPC division was ordered to dismiss the validity claim as inadmissible.

• Practical Outcome: The German judgment remains effective; the UPC cannot reopen the validity issue.

How Does This Affect You?

Before the decision, parties could argue that the UPC’s exclusive jurisdiction allowed a second validity review even after a national court had ruled. The appellate panel clarified that the UPC must respect the res judicata rules of the Member State where the earlier judgment was rendered. Consequently, litigants now have greater certainty that a national decision will preclude a parallel UPC challenge, but they also face the risk of being locked into that national outcome.

For Lawyers & Advocates

• Review all pending UPC filings to identify any parallel national proceedings and advise clients to consolidate or stay actions where a national judgment exists.

• Amend client patent‑licensing agreements to include clauses that trigger mandatory arbitration or settlement if a national court has already ruled on validity.

• Cite this judgment as precedent when opposing a counterpart’s attempt to relitigate validity in the UPC after a German decision, emphasizing Art. 113(1) of the UPC Agreement.

• Advise German patent owners that the risk of an adverse national judgment now extends to UPC strategy, prompting earlier settlement considerations.

• Highlight that the ruling does not affect the UPC’s competence over infringement; therefore, continue to pursue infringement claims in the UPC even when validity is barred.

For Law Students

The case illustrates how the UPC balances its exclusive competence with the autonomy of national procedural rules.
The core doctrinal distinction concerns the interaction between Art. 113(1) (national procedural autonomy) and Art. 115(1) (UPC exclusive jurisdiction).
The decision is particularly relevant for the study of:

• EU patent law and the UPC framework

• Conflict of laws and res judicata principles

• Comparative analysis of national patent statutes versus supranational regimes

• Procedural aspects of cross‑border intellectual‑property litigation

• The role of Article 113 in preserving Member State procedural sovereignty

The decision is comparable to C‑370/15 Huawei Technologies (2019) and C‑673/20 Société BASF (2022); contrasting them shows how courts delineate the limits of EU‑wide jurisdiction when national procedural safeguards are at stake.

For Businesses

• Companies relying on German patents must reassess their enforcement strategy, ensuring that any UPC action does not duplicate a validity challenge already decided in Germany, or risk dismissal.

• CFOs should review the portfolio of patents subject to parallel litigation and consider reallocating resources from UPC validity contests to infringement enforcement.

• In‑house counsel must update internal patent‑litigation checklists to include a step verifying the existence of national judgments before filing UPC validity claims.

• Firms in the automotive and electronics sectors, which frequently use unitary patents, should inform product‑development teams that a German validity ruling now provides de facto protection against UPC re‑examination.

Key Takeaways

• National procedural law now expressly precludes a second UPC validity challenge after a domestic judgment, clarifying the scope of Art. 113(1) of the UPC Agreement.

• Patent litigators must screen for existing national judgments before initiating UPC validity proceedings and adjust client strategies accordingly.

• National courts retain the power to apply their own res judicata rules, while the UPC cannot override those procedural bars.

• Monitor the European Commission’s forthcoming review of the UPC Agreement’s competence provisions, scheduled for early 2027, for possible amendments to Art. 113.

• General counsel should audit all active patent disputes by 31 December 2026 to ensure compliance with the new admissibility standard and avoid dismissed filings.

Source: UPC Says National Laws Govern Repeat Patent Challenges