Written by: Haim Ravia, Dotan Hammer
On September 29, 2026, the U.S. Court of Appeals for the Third Circuit affirmed the District of Delaware’s partial summary judgment in Thomson Reuters Enterprise Centre GmbH v. ROSS Intelligence Inc., holding that Westlaw’s editorial headnotes are protected by copyright and that ROSS’s use of them to train an AI-powered legal research tool was not fair use. The unanimous opinion is a significant appellate ruling on fair use in the context of training an AI system on copyrighted works.
ROSS developed an AI search engine that returns relevant passages from judicial opinions in response to users’ legal questions. To train it, ROSS engaged a contractor to prepare approximately 25,000 “bulk memos” pairing legal questions with passages from opinions, and many of those questions were drawn from Westlaw headnotes. ROSS marketed its product at prices in line with Westlaw’s, and some law firms switched from Westlaw to ROSS. The district court held that ROSS’s use of 2,243 headnotes infringed Thomson Reuters’ copyrights and was not fair use, and certified two questions for interlocutory appeal: whether the headnotes and the Key Number System are original, and whether ROSS’s use was fair.
On originality, the Third Circuit applied the low threshold set by the Supreme Court in Feist and held that the headnotes reflect independent editorial choices about which legal points to extract and how to express them concisely. The court rejected ROSS’s argument that headnotes are uncopyrightable “law,” stating that headnotes are not law; judicial opinions are, and the opinions themselves remain free for anyone to use. It also rejected ROSS’s merger argument, because there are many ways to express points of law drawn from opinions. The court did not decide the originality of the Key Number System, which ROSS had not challenged.
On fair use, the court found that the first, third, and fourth factors weighed against ROSS, while the second factor slightly favored it. Applying the Supreme Court’s decision in Andy Warhol Foundation v. Goldsmith, the court found that ROSS’s use was commercial and served the same purpose as the original, namely building a legal research platform, making it minimally transformative at best. The court distinguished the intermediate-copying cases, such as Sega, Connectix, and Google v. Oracle, because ROSS could have used the judicial opinions directly, observing that ease is not a justification for copying. On market harm, the court held that ROSS appropriated the headnotes’ value for finding and analyzing opinions, and usurped Thomson Reuters’ opportunity to enter a rapidly developing market for licensing headnotes as AI training data. The court also noted evidence that ROSS at times acted in bad faith, including by accessing Westlaw through other users’ credentials.
Importantly, the court framed the case narrowly, describing it as no more than an ordinary copyright case. It emphasized that ROSS’s tool does not generate new content but only returns existing text, and that ROSS was building a direct commercial substitute for Westlaw. In a footnote, the court expressly stated that the arguments regarding generative AI training, raised in the litigation against OpenAI and drawing on Bartz v. Anthropic, do not apply to this case.
Click here to read the Third Circuit’s opinion.
