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Judge Bibas reverses himself and rules that ROSS's use of Westlaw headnotes to train a legal-research AI infringed Thomson Reuters' copyrights and was not fair use

On Feb. 11, 2025, Judge Stephanos Bibas, sitting by designation, revised his 2023 summary-judgment ruling and granted Thomson Reuters partial summary judgment on direct infringement and on fair use, while denying ROSS's cross-motions. He held that Westlaw headnotes are original works, both as a compilation and individually, and that ROSS infringed 2,243 headnotes it had turned into training questions through a contractor, with only the questions of whether some headnotes were verbatim copies of opinions and whether registrations were timely left for trial. On fair use, he found ROSS's purpose commercial and not transformative, since it used the headnotes to build a competing legal search tool, and found the fourth factor favored Thomson Reuters because of harm to the market for its headnotes and to a potential market for AI training data. The opinion opens by saying "a wise man knows when he is wrong" and stresses that only non-generative AI was before the court. The Third Circuit affirmed on Sept. 29, 2026.