US appeals court rules AI training on copyrighted work is not fair use

The U.S. Court of Appeals for the Third Circuit sided with Thomson Reuters against Ross Intelligence, ruling copying copyrighted material to build AI training data was not fair use. The judgment affirms the 11 February 2025 Delaware order and orders Ross to pay Thomson Reuters’ costs on appeal. Thomson Reuters, owner of Westlaw, sued Ross in 2020 over Westlaw's headnotes.