The US Court of Appeals for the Third Circuit affirmed a grant of partial summary judgment in favor of Thomson Reuters, finding that Westlaw’s editorial headnotes were copyrightable and that use of those headnotes to train an artificial intelligence (AI) legal-research platform did not constitute fair use. Characterizing the dispute as “no more than an ordinary copyright case,” the Court emphasized that its decision did not resolve broader questions concerning generative AI training. Thomson Reuters Enterprise Centre GmbH v. ROSS Intelligence Inc., Case No. 25-2153 (3d Cir. Sept. 29, 2026) (Restrepo, Montgomery-Reeves, Bove, JJ.)
Thomson Reuters operates Westlaw, a legal-research platform that provides judicial opinions accompanied by editor-written headnotes summarizing key points of law. Although judicial opinions are not copyrightable, Thomson Reuters claimed copyright protection in the headnotes, which its editors prepare under detailed guidelines requiring them to identify and summarize significant legal principles in concise standalone statements.
ROSS developed a non-generative-AI legal-research platform designed to respond to users’ legal questions by identifying relevant passages from about 10 million judicial opinions. To train its platform, ROSS retained LegalEase Solutions to prepare about 25,000 memoranda, each containing a legal question and four to six responsive judicial opinions. LegalEase used thousands of Westlaw headnotes to formulate the questions. ROSS intended to compete directly with Westlaw and marketed its platform at comparable prices.
Thomson Reuters sued ROSS for copyright infringement. The district court granted partial summary judgment, finding that 2,243 headnotes identified by Thomson Reuters’ expert were sufficiently original to warrant copyright protection and that ROSS’s use of those headnotes was not fair use. The district court certified the originality and fair use issues for interlocutory appeal.
The Third Circuit first addressed copyrightability. Applying the “extremely low” originality threshold established in the Supreme Court’s 1991 Feist Publications, Inc. v. Rural Telephone Service Co. decision, the Third Circuit concluded that the headnotes contained sufficient creativity because editors exercised judgment in selecting which legal principles to summarize and how to express them. The Third Circuit rejected ROSS’s argument that copyright protection would effectively grant Thomson Reuters a monopoly over the law, explaining that judicial opinions remained freely available. The Court also rejected ROSS’s merger doctrine argument, finding that the underlying legal principles could be expressed in many ways.
Turning to fair use, the Third Circuit considered the four statutory factors under 17 U.S.C. § 107:
- As to the purpose and character of the use, the Court found ROSS’s use commercial and, at most, minimally transformative because both platforms served the same purpose, which was helping users locate relevant legal materials. Although ROSS used the headnotes to train its AI platform rather than displaying them, it could have relied on freely available judicial opinions instead. This factor weighed against fair use.
- The nature of the copyrighted work weighed slightly in ROSS’s favor because the headnotes primarily conveyed factual information and legal principles. The Court noted, however, that this factor generally carries limited weight.
- The amount and substantiality of the portion used weighed against fair use because ROSS copied entire headnotes without a sufficiently transformative justification. The Court rejected ROSS’s argument that the copied material represented only a small fraction of Thomson Reuters’ headnote collection, explaining that each headnote was independently copyrightable.
- The market effect factor weighed against fair use because ROSS used the headnotes to develop a competing legal-research platform, threatening Westlaw’s existing market and Thomson Reuters’ potential market for licensing headnotes as AI training data.
With three of the four factors weighing against fair use, the Third Circuit affirmed partial summary judgment for Thomson Reuters. The Court emphasized that its holding was limited to the non-generative-AI system at issue, leaving broader questions concerning generative AI training unresolved.
