ROSS Intelligence Asks Full Third Circuit to Rehear Westlaw Headnote AI Fair Use Ruling

Published November 4, 2026

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Why it matters

ROSS Intelligence has asked the full Third Circuit to rehear a September ruling that its use of Thomson Reuters' Westlaw headnotes to train a legal research AI was not fair use. The petition, filed November 3, 2026, seeks rehearing en banc, which would have the court's entire active bench review the panel decision. ROSS argues that "the panel distorted copyright law in the process of applying it to novel AI technology" and that the ruling conflicts with Supreme Court, Third Circuit, and other circuit precedent. The September 29 panel decision affirmed a district court ruling in Thomson Reuters' favor. The court held that 2,243 headnotes are original enough for copyright protection and that ROSS's copying was not fair use. It called ROSS's use "minimally transformative, at best," because ROSS served the same ultimate purpose as Thomson Reuters, and found that ROSS "usurped Thomson Reuters's opportunity to enter that derivative market" for licensing headnotes as AI training data. The case began in May 2020. Judge Stephanos Bibas, sitting by designation, granted partial summary judgment on February 11, 2025, and the Third Circuit heard oral argument on June 11, 2026. ROSS is now defunct.

Several matters remain open. Thomson Reuters' tortious interference claim is still pending, as are any issues involving headnotes beyond the 2,243 resolved on summary judgment. The court has not yet acted on the rehearing petition. The opinion was initially filed under seal, which limits how fully its reasoning can be cited at this stage.

For attorneys, the stakes are the reach of the ruling. It is the first federal appellate decision on fair use in AI training, and the Third Circuit stated that concerns raised in a separate generative AI case do not apply to ROSS. Practitioners advising AI developers, data licensors, or publishers of editorial material should track whether the full court takes the case, since a denial would leave the panel opinion as the leading appellate word on market harm and licensing-based AI training. Watch also for the tortious interference claim and any further unsealing of the opinion.