First Major AI Copyright Case In U.S. Finds Infringement

On February 11, 2025, in Thomson Reuters Enterprise Centre GMBH and West Publishing Corp., v Ross Intelligence Inc., No.1:20-cv-613-SB, the United States District Court for the District of Delaware ( the “Court”) granted summary judgment for Thomson Reuters on its direct copyright infringement claims and related arguments denying fair use made against the artificial intelligence (AI) based legal research platform, Ross Intelligence Inc. (“Ross”).

The Plaintiff, Thomson Reuters, offers a legal research platform called Westlaw, which contains materials to assist in legal research, such as caselaw and statutes.  The Defendant, Ross, operates a competing legal research platform that uses AI. Thomson Reuters filed a lawsuit against Ross in 2020, alleging that Ross had infringed on its copyright, by using its copyrighted Westlaw headnotes among other materials to train its AI platform. Ross claimed fair use, among other defences.

In 2023, the Court largely denied Thomson Reuters’ motions for summary judgment on copyright infringement and fair use. However, the Court subsequently invited the parties to renew their summary judgment briefings; both parties later filed renewed motions for summary judgment.

The Court first addressed the issue of copyright infringement, finding that Westlaw’s headnotes were original works and Ross had directly infringed over two thousand of Westlaw’s headnotes.

The Court then considered the four-factor test to determine whether fair use applied:  

1. Purpose and Character of the Use: The Court ruled in favour of Thomson Reuters, concluding Ross’s use was commercial and not transformative.

2. Nature of the Work: The Court ruled in favour of Ross, finding that Westlaw’s headnotes were “not that creative”.

3. Amount and Substantiality of the Work Taken: The Court ruled in favour of Ross since Ross used the headnotes to train its AI legal search tool but did not make Westlaw headnotes available to the public.

4. Effect on the Value or Potential Market for the Copyrighted Work: The Court ruled in favour of Thomson Reuters because Ross’s legal research platform was meant to compete with Westlaw by developing a market substitute.  

The Court concluded that the balance of the factors weighed in Thomson Reuters’ favour because factor two carried less weight than factor four. As a result, the Court (among other things) rejected Ross’s fair use defence and granted summary judgment for Thomson Reuters.

Summary By: Victoria Di Felice