A United States appeals court has rejected Ross Intelligence’s AI training fair use defence over its use of Westlaw material. The Third Circuit affirmed the ruling against Ross on 29 September 2026, in the first federal appellate decision on the question. Its written opinion is under seal, so the reasoning is not yet public.
The question reached the court as an interlocutory appeal, meaning an appeal taken before the case has finished in the trial court. It concerns United States copyright law only. Ross Intelligence shut down its legal research platform in 2021, so the dispute is now about liability, damages and precedent rather than a product on the market.
What the Third Circuit Decided and What It Did Not
The court affirmed the District of Delaware’s summary judgment against Ross on copyright infringement and its rejection of Ross’s fair use defence. It did not decide the whole case.
- Decided: The two questions certified to it — whether the Westlaw material is original enough for copyright, and whether Ross’s use of it was fair use.
- Not decided: Damages, which have not been set.
- Not decided: Any remaining claims and defences left open by the district court’s partial summary judgment.
- Not disclosed: The court’s reasoning, because the opinion is sealed.
Summary judgment is a ruling a court makes without a trial, when it concludes no reasonable jury could find otherwise on the facts presented. Affirming it means the appeals court agreed that outcome was correct on those questions; it is not a jury verdict and it is not a finding on the value of the claim.
Why the Opinion Is Sealed
The Third Circuit issued its judgment on 29 September 2026 but kept the accompanying opinion under seal. Court records list Judge Tamika R. Montgomery-Reeves as the author, sitting with Judges L. Felipe Restrepo and Emil J. Bove. The appeal was argued on 11 June 2026.
Sealing at this stage is usually procedural. Briefing in the case involved confidential business material, and an opinion that discusses it is commonly filed under seal first so the parties can propose redactions before a public version is released. The court has not published a timetable for unsealing, and no reason for the seal has been stated on the public record.
The practical effect matters for anyone following the wider wave of AI copyright litigation. Until the opinion is public, there is an appellate result but no readable appellate reasoning, and reasoning is what other courts would draw on.
The Two Questions That Were on Appeal
The district court certified exactly two questions to the Third Circuit under 28 U.S.C. § 1292(b), the federal provision that allows an appeal mid-case when a controlling legal question is genuinely contestable.
- Originality: Whether the West headnotes and the West Key Number System are original, and so capable of copyright protection. A headnote is a short summary of a point of law that Westlaw’s editors write and attach to a court opinion. The Key Number System is Westlaw’s classification scheme for sorting those points of law by topic.
- Fair use: Whether Ross’s use of the headnotes was fair use. Fair use is the statutory defence that permits some unlicensed copying, assessed against four factors including the purpose of the use and its effect on the market for the original.
Judge Stephanos Bibas, who decided the case in the district court, wrote when certifying that he recognised “there are substantial grounds for difference of opinion on controlling legal issues in this case” and that those issues “have the potential to change the shape of the trial”.
How the Case Reached the Appeals Court
| Date | Step |
|---|---|
| May 2020 | Thomson Reuters sues Ross Intelligence in the District of Delaware, case 1:20-cv-00613 |
| 2021 | Ross shuts down its platform, citing the cost of the litigation |
| 11 February 2025 | Judge Bibas grants partial summary judgment for Thomson Reuters and rejects the fair use defence |
| 4 April 2025 | Bibas grants Ross’s motion to certify the two questions for interlocutory appeal |
| 23 May 2025 | Bibas issues a memorandum opinion explaining the certification |
| 24 June 2025 | The Third Circuit appeal is docketed as No. 25-2153 |
| 11 June 2026 | Oral argument before the three-judge panel |
| 29 September 2026 | The Third Circuit affirms; opinion sealed |
Thomson Reuters Enterprise Centre GmbH is the Thomson Reuters entity that holds the Westlaw rights. Westlaw is its subscription legal research service. Ross Intelligence was a startup building an AI-based legal search tool that competed with it.
What the District Court Found in February 2025
Because the appellate reasoning is sealed, the district court’s published opinion remains the only readable judicial analysis in the case. Judge Bibas found that 2,243 Westlaw headnotes met the originality threshold and that Thomson Reuters held valid copyrights in them, and that the Key Number System also cleared that threshold.
On fair use, the district court concluded that Ross’s use was not transformative, because its product served the same purpose as Westlaw: helping lawyers find relevant case law. It characterised what Ross built as a directly competing product, which weighed against fair use on the market-harm factor.
Ross had used the headnotes indirectly. It commissioned memos derived from them to train a search tool that returned judicial opinions rather than generating text. That distinction — training data derived from copyrighted material, feeding a non-generative search product — is part of why the case sits awkwardly alongside the generative AI disputes it is often grouped with.
What Happens Next
With the certified questions answered, the case returns to the District of Delaware. An interlocutory appeal resolves the specified legal questions and sends the rest back; it does not end the litigation.
Nothing has been decided about how much Ross owes, if anything. Statutory and actual damages, and any remaining issues the February 2025 ruling left open, are matters for the district court. Ross could also seek further review, either from the full Third Circuit or the Supreme Court of the United States; no such filing has been reported as of 29 September 2026.
How Far the Ruling Reaches
This is the first time a United States federal appeals court has ruled squarely on whether training an AI model on copyrighted material is fair use, which is why it has drawn attention well beyond legal publishing. Several limits on its reach are worth stating plainly.
- It binds only the Third Circuit: Delaware, New Jersey, Pennsylvania and the US Virgin Islands. Courts elsewhere may find it persuasive but are not required to follow it.
- The reasoning is unavailable: Other litigants cannot yet cite the analysis, only the outcome.
- The technology differs: Ross built a search tool that retrieved existing opinions, not a model that generates new text. Cases involving generative models raise questions this one did not.
- The material differs: Westlaw headnotes are editorial works written to be sold as part of a research product, and the competing use was aimed at the same customers.
A number of organisations filed amicus briefs supporting Ross before the appeal was argued, reflecting how closely the AI and publishing industries were watching. Other AI cases remain at earlier stages, including the OpenAI matter set for trial in January 2027 and a separate complaint where no class has been certified.
Frequently Asked Questions
What Did the Court Decide About AI Training Fair Use?
The Third Circuit affirmed a district court ruling that Ross Intelligence’s use of Westlaw headnotes to train a legal search tool was not fair use under United States copyright law. The decision was issued on 29 September 2026 and the written opinion is under seal.
Is the Thomson Reuters v. Ross Case Over?
No. It was an interlocutory appeal on two certified questions, so the case returns to the US District Court for the District of Delaware. Damages have not been decided.
Why Can the Opinion Not Be Read?
The Third Circuit filed the opinion under seal when it issued judgment on 29 September 2026. No reason has been stated publicly and no unsealing date has been announced. Sealing pending redaction of confidential material is common in commercial appeals.
Does This Ruling Apply to Generative AI Companies?
It binds only federal courts within the Third Circuit, and it concerned a search tool that retrieved existing court opinions rather than a model that generates text. Other courts may treat it as persuasive, but the sealed reasoning cannot yet be cited.
What Is a Westlaw Headnote?
A headnote is a short summary of a single point of law, written by Westlaw’s editors and attached to a published court opinion. The district court found in February 2025 that 2,243 of them met the originality standard for copyright protection.
