Third Circuit: training a legal research AI on Westlaw headnotes was not fair use
In the first federal appellate ruling on fair use in AI training, the Third Circuit affirmed that ROSS Intelligence infringed Thomson Reuters’ copyrights by using Westlaw headnotes to train a competing legal research tool. ROSS has said it will seek Supreme Court review.
The court found three of the four fair-use factors favoured Thomson Reuters. It treated ROSS’s use as only minimally transformative, because the headnotes were used for the same purpose Westlaw uses them: to improve a legal research service. It identified harm both to the legal research market and to an emerging market for licensing headnotes as AI training data.
Importantly, the court distinguished ROSS’s tool, which returned passages from judicial opinions rather than generating new text, from generative AI systems. The broader generative-AI copyright question remains open.
For lawyers choosing tools: ask vendors where their legal content comes from and whether it is licensed. Our AI Vendor Due Diligence Builder includes those questions.
Sources
General information, not legal advice. Check the primary source and any later developments before relying on this summary.