Appeals court rejects fair-use defence for AI training in Thomson Reuters case
The U.S. Court of Appeals for the Third Circuit has ruled that copying copyrighted material to train an artificial intelligence system is not fair use.
The court sided with Thomson Reuters, owner of the legal research platform Westlaw, against Ross Intelligence, a now-closed legal search start-up. The judgment affirms a Delaware federal court order of 11 February 2025 and orders Ross to pay Thomson Reuters' costs on appeal, according to Music Business Worldwide.
Thomson Reuters sued Ross in 2020. It said Ross copied Westlaw headnotes, short editorial summaries of legal points decided in court opinions, and used material derived from them to train a competing AI-powered legal search engine.
Judge Stephanos Bibas granted partial summary judgment to Thomson Reuters on 11 February 2025 and rejected Ross's fair use defence. Fair use is the United States legal doctrine that can allow limited use of copyrighted work without permission.
Judge Bibas then sent two questions up for appeal: whether the headnotes and West's Key Number System are original enough for copyright, and whether Ross's use was fair use.
The appeal drew attention from music business organisations. The Recording Industry Association of America and the National Music Publishers' Association filed a joint amicus brief, a submission by outside groups with an interest in a case, on 25 November 2025. The two bodies said training an AI model on copyrighted works to build a competing service cannot qualify as fair use.
Ross is already gone. It closed its platform in 2021, citing the cost of the litigation. It had warned the appeals court that the outcome would have sweeping consequences for innovation, Courthouse News Service reported last year.
The new opinion runs to 32 pages. It is marked precedential, which means it can be cited as binding law in future cases in that circuit, and was written by Judge Tamika Montgomery-Reeves, sitting with Judges Luis Felipe Restrepo and Emil Bove. The Third Circuit is based in Philadelphia.
The full reasoning is not yet public. The opinion was filed under seal, with an order giving both sides 10 days to propose redactions before the court decides whether to unseal it.
What makes this stand out for music readers is the crossover. A dispute about legal summaries has become a reference point for songwriters, labels and publishers watching how courts treat AI systems trained on copyrighted songs, recordings and lyrics.
