Anthropic Wins: Training AI on Books Is Fair Use, but Piracy Isn't

A federal judge has issued the first substantive ruling on one of the AI industry's biggest legal questions: whether training language models on copyrighted books, without authors' permission, qualifies as fair use. Judge William Alsup says yes — at least in Anthropic's case.

The decision comes in Bartz v. Anthropic, a class-action lawsuit brought by authors against the company behind Claude. It's the first time a court has credited the argument AI giants have been making for years: that training a model on copyrighted works falls under fair use, the legal doctrine that allows protected material to be used without the rights holder's permission under certain conditions.

What the ruling actually means

Fair use is one of the slipperiest concepts in U.S. intellectual property law, and it hasn't been updated since 1976 — long before the internet existed, let alone the notion of training datasets for generative AI. Courts weigh several factors when deciding whether a use is legitimate: what the work is being used for (parody or education tend to get more latitude), whether there's direct commercial gain from the reproduction itself (you can write fan fiction based on a copyrighted saga, but you can't sell it), and above all, how transformative the result is compared to the original.

Alsup found that Anthropic's training of its models on published books was transformative, in line with the standard reasoning applied to language models: the idea that these systems don't simply reproduce the works, but use them to generate new content. That's the exact argument companies like Meta have made in their own defenses against similar lawsuits, and until now it was far from clear whether any judge would back it with a ruling of this weight.

The decision doesn't bind other judges in the dozens of pending lawsuits against OpenAI, Meta, Midjourney, Google, and others. But it does set a precedent: for the first time, a court has put in writing that training itself can be shielded by fair use, giving AI companies a real legal foothold against authors, artists, and publishers who have spent years trying to block the practice in court.

The other half of the case: piracy, no ambiguity

Alsup's ruling doesn't close the Bartz v. Anthropic case. The plaintiff authors didn't just challenge the model's training — they also zeroed in on how Anthropic obtained and stored their works. According to the lawsuit, the company set out to build a "central library" of "all the books in the world" to keep "forever." The problem is that millions of those copyrighted books were downloaded for free from pirate sites, something the law leaves no room to doubt: it's illegal.

Here the judge draws a hard line between the two issues. The fact that training on those books qualifies as fair use doesn't launder the method Anthropic used to acquire them. Alsup has ordered a separate trial on the nature of that "central library" and the damages it may have caused.

In his ruling, the judge put it plainly: "We will have a trial on the pirated copies used to create Anthropic's central library and the resulting damages," he wrote, as reported by TechCrunch. He added a clarification that makes clear buying the book afterward doesn't erase the original offense: "That Anthropic later bought a copy of a book it earlier stole off the internet will not absolve it of liability for theft but it may affect the extent of statutory damages."

Why this distinction matters for the rest of the industry

The ruling draws a line that will likely shape the rest of copyright litigation against AI companies: how a text is used to train a model is one question, and how that text was obtained in the first place is an entirely different one. A company can have solid fair use arguments for training and, at the same time, face legal and financial liability for turning to piracy to gather the material.

For the authors, artists, and publishers who have filed similar lawsuits against other companies, this is a double blow: they lose the core argument over whether training itself is illegal, but they retain a very specific line of attack if they can prove the material was obtained through piracy. For AI companies, the message is just as clear: where training data comes from can matter as much as — or more than — how it's later used.

The trial over Anthropic's "central library" will now determine the real scope of the damages, in a case that already stands as the first serious precedent in the legal battle between the AI training industry and the publishing world.