Court rejects Ross Intelligence's fair-use defence over Westlaw headnotes

Judge Stephanos Bibas, sitting by designation in the District of Delaware, granted Thomson Reuters partial summary judgment against Ross Intelligence, ruling that Ross had infringed copyright by training its legal-research tool on Westlaw’s headnotes. It was the first US ruling to squarely reject an AI company’s fair-use defence over training data, in a case that had been filed in 2020, well before the current wave of generative-AI copyright suits.

Ross was not a generative AI product; it built a legal-search engine that returned relevant judicial opinions in response to natural-language questions, and it had licensed a set of “Bulk Memos” containing Westlaw headnotes to train the underlying model after Thomson Reuters declined to license Westlaw directly. Bibas had denied summary judgment on largely the same facts in 2023, finding factual disputes for a jury, but withdrew that opinion before trial and invited renewed motions — the February 2025 ruling was his reconsidered view.

Working through the four fair-use factors, Bibas found that Ross’s use was commercial and not transformative, since the headnotes were copied “to make it easier to develop a competing legal research tool” rather than for a new purpose; that Thomson Reuters held valid, if thin, copyright in 2,243 of the headnotes at issue; and that the harm to Thomson Reuters’ potential market for licensing data for AI training was itself sufficient to weigh against fair use, regardless of whether Thomson Reuters had built a competing AI tool of its own. Two of the four factors favoured Ross, but Bibas found they did not outweigh the others.

Commentators flagged the ruling’s reasoning on market harm — that foreclosing a licensing market for AI training data alone can defeat fair use — as significant for the many pending suits against generative-AI developers, while noting Ross’s facts (non-generative output, direct commercial substitution) were more favourable to the copyright holder than most of those cases. Ross Intelligence, which had shut down in 2021 citing the litigation’s cost, appealed to the Third Circuit.