In its judgment of the 29th of September 2026, the United States Court of Appeals for the Third Circuit upholds the first-instance decision in the dispute between Thomson Reuters and ROSS Intelligence. The Court recognises that the editorial annotations (headnotes) published on the Westlaw platform are protected by copyright and holds that their use to train an artificial intelligence system cannot benefit from the fair use exception under the US Copyright Act.
The facts
Thomson Reuters, through West Publishing Corporation, manages Westlaw, a legal research platform that collects and organises judicial decisions. The content offered to its users includes headnotes: editorial annotations placed at the beginning of judgments, which summarize the main points of law addressed. Drafting them requires identifying the most relevant legal issues, selecting the necessary factual elements and formulating a clear, self-contained summary in accordance with specific editorial guidelines.
ROSS Intelligence develops a legal search engine based on machine learning, capable of answering questions posed in natural language by identifying relevant passages in judicial decisions. The system is not generative; rather, it identifies extracts from existing judgments. To train it, ROSS engages LegalEase Solutions, which prepares approximately 25,000 memoranda containing legal questions and passages from judgments classified according to their relevance. However, thousands of Westlaw headnotes are used in preparing those memoranda. ROSS also intends to market its service in direct competition with Westlaw. Thomson Reuters therefore files for copyright infringement proceedings. The United States District Court for the District of Delaware rules in favour of Thomson Reuters by way of partial summary judgment, finding that the use of 2,243 headnotes infringes copyright and is not justified by fair use. The dispute comes before the Third Circuit Court of Appeals, which is called upon to rule on the originality of the headnotes and the lawfulness of their use.
Originality
The first issue concerns whether the headnotes should benefit from copyright protection. Under Section 102(a) of the Copyright Act, original works of authorship are eligible for protection. According to the criterion established by the Supreme Court in Feist Publications v. Rural Telephone Service (1991), it is sufficient for a work to have been independently created and for it to possess a minimal degree of creativity.
The Court believes this requirement met because the editors do not merely reproduce the content of the judgments but make independent choices when identifying the principles to be highlighted, selecting the relevant facts and formulating the summaries. The requirement that each annotation be understandable even without consulting the underlying decision further confirms the creative nature of the editorial work. This does not, however, mean that the publisher is granted an exclusive right over judicial decisions or the legal principles they contain: judgments remain freely available for use. Copyright protection applies instead to the specific editorial treatment. The Court rejects the argument based on the merger doctrine, according to which protection is unavailable where an idea can be expressed in one or a few ways. The Court observes that the same legal principles can be summarised in different ways of expression.
Fair use
The second issue concerns the exception provided for in Section 107 of the Copyright Act: fair use. The Court assesses four factors: the purpose and character of the use; the nature of the copyrighted work; the amount and substantiality of the portion used; and the effect on the actual or potential market.
In the present case, only the second factor favours ROSS. The headnotes, in fact, have a predominantly factual and functional component, since they are intended to accurately represent the content of the decisions.
The other three factors, by contrast, lead the Court to rule out fair use. In regard to the first factor, ROSS’s use is commercial and only minimally transformative: both systems use the annotations to improve legal research and identify relevant materials. According to the Court, the fact that ROSS uses them as an intermediate step in training its system does not change the substantive function of that use. Moreover, the system intends to offer a product that would serve as a substitute for Westlaw.
In regard to the third factor, ROSS argues that it used only 0.08% of the approximately 28 million available annotations. The Court observes, however, that each headnote constitutes an independent work: reproducing its text in full therefore amounts to copying the entire work.
Finally, the Court finds that the use causes harm to the market for legal research services and to the potential market for licences to train AI systems. It is not decisive that Thomson Reuters is not granting licences of this kind yet, since the potential market may also include uses that the rights holder could reasonably develop or authorise.
In the final decision of the Court, the three factors weighing against ROSS prevail over the sole factor in its favour. The Court therefore upholds the first-instance decision: the use of the headnotes does not fall within the fair use exception.
The judgment does not establish a general prohibition on using protected materials to train artificial intelligence systems. Rather, it reiterates that such use must be assessed on a case-by-case basis, taking into account the nature of the materials, the purpose of the use, the extent of the reproduction and the consequences for the rights holder.
