On June 23, 2025, Judge Alsup in the Northern District of California issued an order in Bartz et al. v. Anthropic PBC, granting in part and denying in part Defendant Anthropic’s motion for summary judgment on the sole issue of whether its use of Plaintiffs’ books as training data for Anthropic’s large language models (LLMs) was “quintessential” fair use.

Central to its mixed holding, the court acknowledged that Anthropic used the works in various ways and for varying purposes, such that each “use” must be identified and assessed separately. Ultimately, the court held that while the use of textual works to train LLMs was “exceedingly transformative” and thereby was protected as fair use when considered against the remaining factors, the separate use of the works to create a central library was only fair use with respect to works purchased or lawfully accessed—i.e., the use of pirated copies to create the central library was not protectible fair use. This decision makes clear that the source of content is a key element in evaluating fair use.