Thomson Reuters: Legal AI and the ROSS Copyright Case

Legal information as product and training material

Thomson Reuters combines professional information with software. CoCounsel Legal brings legal research, document analysis and drafting workflows together with Westlaw, Practical Law and a firm’s own documents. [1][2]

In the February 2025 ROSS decision, Thomson Reuters Enterprise Centre and West Publishing were the actual plaintiffs. The dispute concerned Westlaw headnotes used in developing a competing legal search system, rather than ownership of judicial opinions themselves. The district court granted partial summary judgment, including rejecting ROSS’s fair-use defense for the headnotes at issue. [3]

The September 2026 appeal affirmed that limited ruling on an interlocutory appeal. The opinion addresses 2,243 headnotes and distinguishes ROSS’s non-generative retrieval tool from systems that create new expression. It is an important training-data decision without being a universal holding about generative AI or a resolution of every claim and remedy. [4]