The Third Circuit’s opinion in Thomson Reuters v. ROSS Intelligence, filed on 29 September and unsealed on 30 September, is now public. The court affirmed the district court, writing that it will “AFFIRM the District Court’s order granting Thomson Reuters partial summary judgment”. Judge Montgomery-Reeves wrote for the panel (No. 25-2153).
The reasoning is what matters. ROSS had copied the full text of 25,000 Westlaw headnotes to build a legal research tool. On the first fair use factor the court found the use “highly commercial” and “minimally transformative, at best”, since both companies were building legal research platforms, and rejected the analogy to search indexing: “ease is not a justification for copying”. Only the second factor, the factual nature of headnotes, leaned the other way, and only slightly.
The fourth factor is the part other AI cases will cite. The court held that ROSS harmed not just the existing market but a developing one for licensing the headnotes as training data: by copying them, “ROSS usurped Thomson Reuters’s opportunity to enter that derivative market”.
A caution on scope. ROSS built a search tool over headnotes, not a generative model, so the facts are narrower than the pending suits against frontier labs. But the derivative-market holding is the first appellate statement that an AI training licence is a protected market.