In Thomson Reuters Enterprise Centre GmbH v. ROSS Intelligence Inc., Thomson Reuters and West Publishing sued a legal-technology start-up for copying Westlaw editorial content to build a competing AI search product. On 29 September 2026 the United States Court of Appeals for the Third Circuit affirmed a ruling for Thomson Reuters on the two certified questions: the Westlaw headnotes at issue were original enough for copyright, and ROSS’s use of them was not fair.[1] The case concerns copyright in a vendor’s content, not a software licence dispute, but it is the clearest court statement on how Thomson Reuters content may be used to train AI, which is also a clause of its contracts.
Background
The court describes Westlaw as an online legal-research platform that collects, organises, annotates and publishes legal content such as judicial opinions. Westlaw organises opinions with its topic and Key Number System, which connects to headnotes, annotations that explain what the law is in the abstract or the result it compels on the facts of the case.[1] Thomson Reuters owns a registered copyright in Westlaw and its content, including the Key Number System, headnotes and synopses, while disclaiming copyright in work prepared by government officers or employees such as the underlying opinions.[1] Editors follow guidelines under which each headnote must be clear, concise and able to stand alone, with a target length of 800 characters where possible.[1]
ROSS was founded by three University of Toronto students who entered an IBM Watson competition, and it built an AI legal search engine that responds to plain-language legal questions with passages from judicial opinions. The court says ROSS’s AI was not generative: it returned only passages from existing opinions and created no new expression.[1] To train it, ROSS engaged LegalEase Solutions, which wrote about 25,000 legal memoranda, each presenting a legal question and four to six opinion passages. LegalEase and its subcontractor Morae Global used thousands of Westlaw headnotes to create the memoranda’s questions because the headnotes provided “an easy way” to frame them.[1] ROSS advertised its platform against Westlaw at prices “in line with” Westlaw, and some law firms switched from Westlaw to ROSS.[1]
Procedure
Thomson Reuters sued ROSS for copyright infringement and tortious interference with contract. The United States District Court for the District of Delaware (Judge Stephanos Bibas, sitting by designation) granted partial summary judgment for Thomson Reuters, holding as a matter of law that ROSS’s use of 2,243 Westlaw headnotes infringed and was not fair use. At the parties’ request the District Court then certified for interlocutory review whether the West headnotes and the Key Number System are original as a matter of law and whether ROSS’s use of the headnotes was fair use.[1] The Third Circuit heard the appeal under 28 U.S.C. section 1292(b) on 11 June 2026 and filed its opinion on 29 September 2026.[1] ROSS did not challenge the originality of the Key Number System in its briefing, so the court treated that point as forfeited and did not decide it.[1] ROSS also did not dispute on appeal that the actions of LegalEase and Morae Global were attributable to ROSS or that they copied Westlaw headnotes.[1]
Decision
Originality
The court applied the “extremely low” originality bar of Feist. It held that all 2,243 headnotes have some creative spark, because editors decided which points of law were important enough to include and how to word them under Westlaw’s drafting criteria, so that each headnote could stand on its own while accurately reflecting the opinion.[1] The court noted that the question of headnotes that quote opinions verbatim was not answered, because summary judgment covered only headnotes that do not copy opinion text verbatim.[1]
Fair use
The court weighed the four statutory factors and concluded that the second factor weighed slightly in favour of fair use, while the first, third and fourth weighed against it.[1]
| Factor | Finding |
|---|---|
| Purpose and character | ROSS’s use was commercial and, at best, minimally transformative: it used headnotes to train an AI program for a legal-research platform with the same ultimate purpose as Westlaw’s use of headnotes. Copying was not necessary, because ROSS had the freely available opinions and chose the headnotes because it was “easy”. The opinion states that, unlike necessity, ease is not a justification for copying.[1] |
| Nature of the work | Favoured fair use slightly.[1] |
| Amount used | Weighed against fair use: the purpose was minimally transformative and copying the headnotes was not necessary, so ROSS took more than necessary, and each headnote taken was an entire copyrightable work.[1] |
| Market effect | Weighed against fair use: the evidence showed a rapidly developing market for licensing headnotes as AI training text, and ROSS usurped Thomson Reuters’s opportunity to enter it, although Thomson Reuters had not licensed its headnotes to others.[1] |
The court distinguished software-interface cases such as Google v. Oracle, Sega v. Accolade and Sony v. Connectix, where code was copied to make software operable with an existing system and the copying was necessary to reach unprotected functional aspects; it said ROSS did not need the headnotes to access the unprotected information.[1] It also stated that ROSS’s AI could not generate original expression, so that the reasoning does not decide questions about generative AI training.[1]
The court concluded that the headnotes are original enough for copyright protection and the use was not fair, and it affirmed.[1]
Connection to Thomson Reuters licensing
The opinion is a copyright ruling, but the same behaviour is addressed in the contract. The Thomson Reuters General Terms bar a customer from using the Property to develop, train, adapt, fine-tune, modify or improve any artificial intelligence software or other technologies.[2] For licence managers the case shows that this restriction is backed by a judicial view of what Westlaw editorial content is, and that a subscription gives access to use the service, not a right to build training data from it. See Westlaw, Practical Law and CoCounsel Legal licensing and CoCounsel and generative AI terms.
Lessons learned
- Editorial content can carry its own copyright. The court found creative decisions in headnotes sufficient for copyright, although the opinions they summarise are free to copy.[1] A licence inventory of information services should therefore treat editorial layers as protected content.
- Access is not a training licence. Thomson Reuters’s terms separately prohibit training AI on its Property, and the market-harm finding rested on a developing market for licensing headnotes as training data.[2][1]
- Contractors act for the customer. LegalEase and Morae Global wrote the memoranda, and the copying was attributed to ROSS on appeal without challenge.[1] Subcontracted data preparation needs the same content controls as internal work.
- Competing use weighs against fair use. ROSS marketed a substitute for Westlaw at comparable prices, and the court found the use commercial and minimally transformative.[1]
- Necessity matters. The opinion contrasts the software-interface cases, where copying was necessary, with ROSS, which copied because it was easier.[1]
Status
This was an interlocutory appeal certified by the District Court, and the Third Circuit’s opinion affirmed the partial summary judgment.[1] The opinion does not describe the state of the remaining claims in the District Court, and later proceedings, including any rehearing request or petition for review, should be checked against the court’s docket.