Authors Guild and Leading Writers’ Organizations File Amicus Brief in Support of Authors in Class Action Against Anthropic

On August 21, 2025, the Authors Guild, along with International Thriller Writers, the Science Fiction and Fantasy Writers Association, and Romance Writers of America, filed an amicus brief in the Ninth Circuit Court of Appeals urging the court to reject Anthropic’s petition to appeal class certification in the ongoing copyright infringement case against the company.

The brief explains that Anthropic engaged in large-scale piracy of copyrighted books, downloading them from illegal repositories such as Library Genesis (LibGen) and Pirate Library Mirror (PiLiMi) to train its AI models. The District Court found that these claims present common questions of law and fact, and that they are best resolved on a class wide basis.

In the brief, the Guild and other amici challenge Anthropic’s petition against class certification, explaining that it is entirely feasible to notify authors or determine who holds the reproduction rights to the works at issue. We emphasize that because most of the pirated works are recently published ebooks, publishers and rightsholders can be readily identified through copyright registration data, ISBN/ASIN numbers, and standard industry records. Further, the court-approved notification process—supplemented by ongoing outreach from authors’ groups, publishers, agents, and collective licensing entities—will ensure that writers are effectively informed of their rights.

The brief also emphasizes that authors and publishers have long collaborated to fight piracy and that hypothetical disputes over copyright ownership are rare, manageable, and already contemplated in publishing agreements. Far from being unworkable, the class process provides a practical and efficient way to address infringement on such an enormous scale.

Read the full brief here (PDF).

Find other important info for authors about the Anthropic case here.