ROSS Intelligence built its natural-language search platform in 2015 by converting over 2,200 Westlaw headnotes into training questions for its AI system. Thomson Reuters, which owns the copyright in those headnotes, denied ROSS's license request and sued for infringement. A Delaware federal court granted summary judgment to Thomson Reuters in February 2025, finding the use non-transformative and commercially harmful. ROSS appealed. The Third Circuit is expected to rule in late 2026.
Attorneys should monitor this case closely. It is the first federal appellate decision squarely addressing whether using copyrighted works to train AI models qualifies as fair use. The panel's focus on market harm—including potential substitution for Westlaw, Thomson Reuters' own exclusive training rights, and a licensing market for headnotes—suggests the court is treating this as a test case for the entire legal-AI sector. The outcome will likely govern how legal-tech companies can use third-party content to develop new research tools.