More than 10,500 creative professionals, including Thom Yorke from Radiohead, actress Julianne Moore, and Nobel Prize-winning author Kazuo Ishiguro, have signed an open letter against the “unlicensed use of creative works” for developing AI systems like OpenAI’s ChatGPT.

The letter, which is just 29 words long, states that using creative work without permission is a serious threat to the livelihoods of the creators and should not be allowed.

The Statement on AI training states, “The unlicensed use of creative works for training generative AI is a major, unjust threat to the livelihoods of the people behind those works, and must not be permitted.”

AI companies need various types of content—like text, images, and videos—to train their systems. Often, this content is taken from the internet without consent or payment. While tech companies argue this is “fair use” under copyright law, many creators and publishers are fighting back, claiming that their rights are being violated.

Ed Newton-Rex, a former AI executive and music composer who helped organize the letter, emphasized the importance of addressing creators’ rights now. He mentioned that high-profile lawsuits against AI companies are currently in progress. Regulators in the U.S. and the U.K. are also discussing whether to create copyright exemptions for AI projects.

The letter has support from many well-known figures, including actors Kevin Bacon and Melissa Joan Hart, comedians Kate McKinnon and Rosie O’Donnell, and several award-winning composers. Fairly Trained, the nonprofit behind the letter, certifies tech companies for their data practices that respect creators’ rights.

Protests against unauthorized use of creative work for AI have also included artists like Billie Eilish and Nicki Minaj, as well as a group of over 15,000 authors, including Margaret Atwood and Jonathan Franzen.

While courts are allowing some lawsuits against AI companies to proceed, proving copyright infringement can be difficult. Some content publishers have chosen to work with AI developers by signing agreements that allow access to their data for payment.