New to this? Read it in simple words
- A company called Ross used legal summaries from Westlaw to train its AI search tool.
- Westlaw’s owner, Thomson Reuters, said this broke copyright law and went to court.
- A US appeals court agreed with Thomson Reuters, the first such ruling on AI training.
- The judges’ full reasons are secret for now and will be published later.
- Fair use
- A US rule that allows some use of copyrighted work without permission.
- Appeals court
- A higher court that checks whether a lower court decided correctly.
- Sealed
- Kept private by the court, at least for a time.
Thomson Reuters sued Ross Intelligence in 2020, saying the start-up had copied Westlaw’s headnotes, short summaries of points of law, to train an AI legal search engine. A federal judge in Delaware rejected Ross’s fair use defence last year, and Ross appealed.
What the court decided
On September 29, three judges of the US Court of Appeals for the Third Circuit affirmed the lower court’s judgment, the court’s docket shows. Judge Montgomery-Reeves wrote the 32-page opinion, with Judges Restrepo and Bove on the panel.
The ruling rejects Ross’s argument that its use of the material was fair use, Reuters reports. It is the first time a US appeals court has ruled on fair use in a dispute over AI training.
The court filed the opinion under seal. It gave the two sides 10 days to propose redactions, with a reason for each, and will then decide how to publish it.
Steps from the court docket and Reuters. The opinion itself is sealed for now.
What the case is about
Ross allegedly used thousands of Westlaw headnotes to train its search engine to find the court opinions that answer a user’s question. Ross shut down its platform in 2021, citing the cost of the lawsuit.
Unlike most AI copyright cases, this one does not involve generative AI, which creates new content. “Ross took the headnotes to make it easier to develop a competing legal research tool,” the lower court judge wrote. “So Ross’s use is not transformative.”
Sources2
Why it matters
Authors, news outlets, music labels and others have filed dozens of lawsuits over the use of their work to train AI. Tech companies argue that training turns the material into something new; copyright owners say the systems compete with their work.
Thomson Reuters said it was pleased with the ruling. Ross and its lawyer did not immediately respond to Reuters. Reuters News is owned by Thomson Reuters, so we checked the outcome against the court’s own docket.
Sources
Every fact in this story comes from the sources below. Open them to check our work.
- 1Primary source · Accessed September 30, 2026Thomson Reuters Enterprise Centre GmbH v. Ross Intelligence Inc, No. 25-2153 (docket) US Court of Appeals for the Third Circuit, via CourtListener
- 2Research · September 29, 2026US appeals court upholds Thomson Reuters’ landmark win in AI training lawsuit Reuters
- 3Research · September 29, 20263rd Circuit Issues Opinion in Thomson Reuters v. ROSS Case, But For Now It Is Sealed LawSites
Reuters is owned by Thomson Reuters, one of the parties, so the outcome here rests on the court’s docket. The court’s reasoning is not public yet.
Appeals court rejects fair use for Ross’s AI training. Silicon AI News, September 30, 2026. https://siliconainews.com/stories/thomson-reuters-ross-appeal-ruling
The first US appeals ruling on AI training and copyright rejected fair use, a setback for training AI on copyrighted work. How we rate the mood
The mood shows how the news frames the event for the tech and AI world: as an opportunity (6 and above) or as a loss (below 5). It is not our verdict on who is right.