Thomson Reuters Emerges Victorious in AI Copyright Battle

• The U.S. District Court for the District of Delaware ruled in favor of Thomson Reuters in a copyright infringement case against Ross Intelligence, finding Ross improperly used Thomson Reuters’ headnotes to train its AI legal research tool. 
• The court emphasized that Ross’ use was commercial and non-transformative, directly competing with Thomson Reuters’ services, which had a significant market impact.  
• The case highlights the importance of ensuring training data is either licensed or publicly available to avoid copyright issues. Businesses using copyrighted data for AI training risk legal consequences.  
• Companies should investigate and monitor potential misuse of copyrighted materials by AI tools, ensure proper licensing for their training data, and secure copyright registration for their content to protect against infringement.

Technology often outpaces the law, but a new copyright infringement decision in the U.S. District Court for the District of Delaware shows that the courts are starting to catch up in regulating artificial intelligence (AI), particularly around the use of certain data for training AI tools.

In Thompson Reuters v. Ross Intelligence, the court ruled in summary judgement that Ross overstepped its bounds by using short summaries similar to Thomson Reuters’ headnotes to train its AI legal research tool. The court found in favor of Thomson Reuters on two of four factors of the “fair use” defense to copyright infringement asserted by Ross and ultimately ruled in favor of Thomson Reuters in regard to copyright infringement, at least for a portion of the total headnotes.

Ross used data similar to headnotes from Thomson Reuters’ Westlaw Keynote System, obtained via “Bulk Memos” from LegalEase, for training its AI tool. It is important to reiterate at this point that the “Bulk Memos” that copied the Westlaw headnotes were not presented to the end-user of Ross’ legal search tool; rather, the “Bulk Memos” were only used for training. After Thomson Reuters sued Ross for copyright infringement, Ross claimed fair use, as well as several other defenses. Interestingly, Judge Stephanos Bibas ruled in 2023 that the AI tool did not infringe upon Thomson Reuters’ copyrights. In this latest ruling, however, the Judge determined, for a portion of the headnotes, that Ross did not meet its burden for fair use and, thus, infringed on Thomson Reuters’ copyrights. The Judge wrote in the February 11, 2025 decision, “[w]isdom does not always find me, so I try to embrace it when it does––even if it comes late, as it did here.”

The court, in granting summary judgment for Thomson Reuters, stated that the headnotes were directly copied and that the headnotes were protectable matter. The Judge stated that “[a] block of raw marble, like a judicial opinion, is not copyrightable. Yet a sculptor creates a sculpture by choosing what to cut away and what to leave in place. That sculpture is copyrightable.” Further, all of Ross’ other defenses failed as well.

In analyzing four of the factors of the fair use defense doctrine, the court ruled in favor of Thomson Reuters, noting that the first and fourth factors analyzed were given the most weight. For the first factor, the court stated that Ross’ purpose was commercial as Ross was producing some end product that utilized the copywritten material. Further, the court ruled that Ross’ use was not transformative as the use of the headnotes was to create a competing legal research tool. The court also noted that, even if there was no bad faith in the use of the “Bulk Memos” and since the use was commercial and non-transformative, the lack of bad faith would not “move the needle” or outweigh this commercial and non-transformative use. For the second factor, the court noted that the headnotes included limited creativity, conceding this point to Ross. For the third factor, while this could be interpreted as favoring neither party nor even Thomson Reuters, the court  found that this factor was in favor of Ross since the final output of the AI tool did not include any of the headnotes, but, rather, included only judicial opinions. Finally, for the fourth factor, the court considered the impact of Ross’ AI tool on the market. Ross’ AI tool directly competed with Thomson Reuters’ services, thus heavily impacting the market for Thomson Reuters. Lending the most weight to the last factor analyzed, the judge, as noted, ruled against Ross and granted summary judgment to Thomson Reuters on direct copyright infringement for at least some of the headnotes.

For those who train models, one should ensure that the data utilized for training are either obtained via a license and/or, at the least, not under copyright (e.g., in the public domain or purely functional). For those who own copyrighted data, some research as to what AI tools are available is recommended. In other words, based on a type of AI tool, one can assume what type of data may have been used to train that tool. Based on the facts in this case, Thomson Reuters knew that Ross was at least attempting to use data similar to their headnotes, as Ross tried to obtain a license to those headnotes via a license agreement. Thomson Reuters refused to grant Ross a license since Ross was a direct competitor. If data that are being used to train an AI tool are suspected to be potentially similar to one’s data, then research and investigation should be performed. Such an investigation may include querying the AI tool and reviewing user manuals or documentation related to the AI tool, among other steps. Finally, ensuring that data are covered by copyright at least enables one to seek copyright registration and protection of their data, should misuse be suspected.