Some of the world’s largest book publishers have jointly filed a lawsuit against Amazon-owned audiobook company Audible today over a new, controversial speech-to-text feature the literary industry claims is a violation of copyright law.

The lawsuit, filed in the Southern District Court of New York, includes the Big Five: Hachette, HarperCollins, Macmillan, Penguin Random House, and Simon & Schuster. It also includes San Francisco-based publisher Chronicle Books and Scholastic, the major children’s publisher that owns publishing rights to Harry Potter and The Hunger Games. All seven plaintiffs are members of the Association of American Publishers.

“Audible’s actions are the kind of quintessential infringement that the Copyright Act directly forbids.”

Publishers are taking issue with Audible’s new Captions feature, first unveiled last month and set to go live in September through partnerships with US public schools. The feature uses machine learning to transcribe spoken words into written ones, so users can read along while they listen to an audiobook. The issue, however, is that Audible is doing this based on audiobook recordings, which have separate licenses to physical books and ebooks. The company is not apparently obtaining the necessary licenses to reproduce the written versions of these works.

Because Audible is relying on artificial intelligence, it appears the company is trying to claim a distinction between a newly created piece of text composed using AI, based on an audio recording, and the potentially near-identical text version of the book the audiobook was created from. (As evidence that the text is generated on the fly, Amazon says its transcriptions may contain errors and are not intended to be complete recereations of the text version of a book.) At the time of its launch, Audible CEO Don Katz positioned Captions as an educational feature designed for schools, telling USA Today, “We know from years and years of work, that parents and educators, in particular, understand that an audio experience of well-composed words is really important in developing learners.”

“Audible’s actions — taking copyrighted works and repurposing them for its own benefit without permission — are the kind of quintessential infringement that the Copyright Act directly forbids,” the complaint reads. “If Audible is not enjoined, Audible will take for itself a format of digital distribution it is not authorized to provide, devalue the market for cross-format products, and harm Publishers, authors, and the consumers who enjoy and rely on books.”

In a statement given to The Verge, Audible defended the development of Captions as an educational feature designed to help young kids and improve literacy, saying “it is not and was never intended to be a book.” An Audible spokesperson also pointed to an explanation of the Captions feature and an attached FAQ penned by Katz in late July, which details the differences between Captions and a proper ebook and the limitations posed on listeners. One key difference, Audible says, is not being able to flip through pages, as users must wait for each line of text to be progressively generated as they’re listening. Here is Audible’s statement in full:

We are surprised and disappointed by this action and any implication that we have not been speaking and working with publishers about this feature, which has not yet launched. Captions was developed because we, like so many leading educators and parents, want to help kids who are not reading engage more through listening. This feature would allow such listeners to follow along with a few lines of machine-generated text as they listen to the audio performance. It is not and was never intended to be a book. We disagree with the claims that this violates any rights and look forward to working with publishers and members of the professional creative community to help them better understand the educational and accessibility benefits of this innovation.”

At the heart of the case will be a determination on the transformative nature of an AI-created audio transcription, and whether that constitutes a violation of the copyrights held on a written work.

“This is one of many lawsuits that will help define the future of intellectual property rights in the digital age. It raises major questions over what impact artificial intelligence, when it interacts with copyrighted material, will have on intellectual property rights,” Sam P. Israel, a copyright attorney and founder of Sam P. Israel P.C., told The Verge over email. “Ultimately, unauthorized reproductions of copyrighted material, even when done unwittingly through the assistance of AI, will likely not pass muster in the courts.”

The case happens to have a strong analog to a former Amazon publishing controversy a decade ago, when the company tried to launch a text-to-speech feature for its Kindle platform that would effectively do what Amazon Captions does today, but in reverse.

Publishers at the time were enraged, accusing Amazon of trying to trample on the nascent audiobook market and the licensing rights that publishers believed would help it become a thriving business. Amazon eventually caved in that regard, allowing publishers to disable the Kindle text-to-speech feature after a massive outcry from the US Authors Guild.

“There is a simple English word to describe this: and that is theft.”

Publishers and the Authors Guild have been putting up a similar fight for the last month. After the feature was announced, the Authors Guild released a statement saying “existing ACX and Audible agreements do not grant Audible the right to create text versions of audio books.” The group said the feature “appears to be outright, willful copyright infringement, and it will inevitably lead to fewer ebook sales and lower royalties for authors for both their traditionally published and self-published books.”

Audible has been mostly quiet about the matter, telling The Verge last month that it did “not agree with this interpretation” from the Authors Guild, but the company formally declined to comment further. Audible also refused to comment about whether it would work with publishers on establishing some form of licensing that would allow the Audible Captions feature to exist while also fairly compensating rights holders.

In a new statement, the Authors Guild expressed support for the lawsuit. “Without authorization and in violation of its contracts with publishers, Audible added a text feature to its audiobooks. Text and audio are different book markets, and Audible is licensed only for audio,” writes Mary Rasenberger, the executive director of the Authors Guild.” It has chosen to use its market power to force publishers’ hands by proceeding without permission in clear violation of copyright in the titles.”

In an interesting twist, some of the books for which Audible has added Captions support are written by Authors Guild President Doug Preston, who was not pleased. “My contract is crystal clear that the only rights conveyed to Audible are for voice recording and playback. The rights to reproduce text in any way are specifically withheld,” Preston said in a statement. “I can’t believe that Audible has so little respect for authors, contractual promises, and copyright that it thinks it can just help itself to rights it doesn’t have, by fiat. There is a simple English word to describe this: and that is theft.”

Update August 23rd, 2:40PM ET: Added statements from the Authors Guild.

Update August 23rd, 5:33PM ET: Added statement from Audible.