US appeals court rules AI training on Westlaw headnotes isn't fair use

The Third Circuit ruled that Ross Intelligence infringed Thomson Reuters' copyrights by training its legal research system on Westlaw headnotes. The court found the headnotes copyrightable and rejected the fair use defense, citing direct competition with Westlaw.

• Court held Westlaw headnotes are protected by copyright
• Use deemed "minimally transformative" due to competition with Westlaw
• Market harm to AI training data licensing weighed in ruling
• Decision does not set a broad rule for all AI training disputes