July 17 (Reuters) - A California federal judge ruled on

Thursday that three authors suing artificial intelligence

startup Anthropic for copyright infringement can represent

writers nationwide whose books Anthropic allegedly pirated to

train its AI system.

U.S. District Judge William Alsup said the authors can bring a

class action on behalf of all U.S. writers whose works Anthropic

allegedly downloaded from "pirate libraries" LibGen and PiLiMi

to create a repository of millions of books in 2021 and 2022.

Alsup said Anthropic may have illegally downloaded as many

as 7 million books from the pirate websites, which could make it

liable for billions of dollars in damages if the authors' case

is successful.

Spokespeople for Anthropic did not immediately respond to a

request for comment on the decision. An attorney for the authors

declined to comment.

Andrea Bartz, Charles Graeber and Kirk Wallace Johnson sued

Anthropic last year, arguing that the Amazon ( AMZN )- and

Alphabet-backed startup used their books without

permission or compensation to teach its chatbot Claude to

respond to human prompts.

The case is one of several high-stakes lawsuits brought by

authors, news outlets and other copyright owners against

companies including OpenAI, Microsoft ( MSFT ) and Meta

Platforms ( META ) over their AI training.

AI companies argue their systems make fair use of copyrighted

material to create new, transformative content. Alsup determined

in June that Anthropic's AI training made fair use of authors'

works, but said the company still violated their rights by

saving pirated copies of their books to a "central library of

all the books in the world" that would not necessarily be used

for AI training.

Alsup said on Thursday the three authors could represent all

writers whose books Anthropic allegedly downloaded from LibGen

and PiLiMi, rejecting Anthropic's argument that identifying all

of the copyright-eligible works and their authors would be

impractical.