The 3rd US Circuit Court of Appeals upheld a copyright ruling for Thomson Reuters against Ross Intelligence on 29 September and rejected Ross’s fair-use defence over material from Westlaw, Reuters reported. The dispute concerns headnotes used to train a legal search engine.
Key points
- The appeals court left intact a Delaware federal judge’s rejection of Ross’s fair-use defence.
- Thomson Reuters accused Ross of copying thousands of Westlaw headnotes to train a competing legal search engine.
- The case concerns legal search rather than generative AI, and the appeals court’s reasoning is sealed.
Westlaw headnotes and Ross’s search engine
Thomson Reuters brought the lawsuit in 2020, accusing Ross of copying Westlaw headnotes — summaries of points of law in court opinions. Its allegation concerned thousands of headnotes that Ross allegedly used to train an AI-based legal search engine. Ross’s product was designed to identify relevant court opinions in response to users’ queries.
The companies disputed the use of material within a legal research market they both served. Thomson Reuters said Ross had taken material from Westlaw for a competing search tool. Ross maintained that using the headnotes to train its system was fair use. Those positions put the purpose of the copying at the centre of the case, alongside the question of whether Ross’s use transformed the material.
Ross shut down its platform in 2021, citing the cost of Thomson Reuters’ litigation. That shutdown came before the judge’s ruling and Ross’s appeal. Thomson Reuters is also the parent company of Reuters News.
Delaware judge rejects Ross’s fair-use defence
A federal judge in Delaware rejected Ross’s fair-use defence in 2025. The judge found that Ross had taken the headnotes to make development of a competing legal research tool easier and held that Ross’s use was not transformative. Ross appealed that ruling, bringing the dispute before the 3rd Circuit.
The court fight sits among dozens of lawsuits brought by authors, news organisations, music labels and other copyright owners over the use of their works to train AI systems. Technology companies have argued that generative AI systems make fair use of training material by transforming it into something new. Copyright owners have argued that the resulting systems can produce competing content.
3rd Circuit ruling concerns legal search
Reuters described the Ross dispute as the first copyright case concerning AI training to reach a US appeals court. Unlike disputes over generative AI, this one concerns a system that searched for relevant opinions in response to a query. Ross relied on fair use for that training, while Thomson Reuters challenged the copying of its headnotes.
The 3rd Circuit’s decision leaves the Delaware ruling in Thomson Reuters’ favour in place. The district judge’s stated reason concerned Ross’s use of the headnotes to develop a competing research product. The appeals court’s reasoning for rejecting Ross’s defence is currently sealed, Reuters reported.
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