A group of artists — Sarah Andersen, Kelly McK­er­nan, and Karla Ortiz — have filed a class-action lawsuit against Midjourney and Stability AI, companies behind AI art tools Midjourney and Stable Diffusion, and DeviantArt, which recently launched its own artificial intelligence art generator, DreamUp.

The suit alleges that these companies “violated the rights of millions of artists” by using billions of internet images to use train its AI art tool without the “consent of artists and without compensating any of those artists.” These companies “benefit commercially and profit richly from the use of copyrighted images,” the suit alleges. “The harm to artists is not hypothetical,” the suit says, noting that works created by generative AI art are “already sold on the internet, siphoning commissions from the artists themselves.”

The three plaintiffs are artists whose work has been used to train these generative AI tools. Andersen is the creator of popular webcomic Sarah’s Scribbles. McK­er­nan is a full-time artist whose works have been featured in galleries and who makes illustrations for comics, books, and games. Ortiz is a concept artist and illustrator whose clients include Marvel Film Studios and Wizards of the Coast.

Attorney Matthew Butterick filed the suit, working with Joseph Saveri Law Firm, a California-based firm specializing in antitrust and class-action law. The Stable Diffusion litigation blog describes Stable Diffusion, and generative AI like it, as “a parasite that, if allowed to proliferate, will cause irreparable harm to artists, now and in the future.”

The group is seeking a jury trial and unspecified damages.

AIgenerated art has grown in prominence since last summer, as tools like Stable Diffusion and Midjourney became available for broad use. And as AI-generated art has become more prominent, artists have pushed back. AI art tools are trained with billions of images from the internet, and artists often don’t have a way of opting in or out. Stable Diffusion, for example, was trained using LAION-5B, a database of 5.85 billion text-image pairs with sources including Flickr, DeviantArt, Wikimedia, and overwhelmingly, Pinterest. Using an AI art tool like Stable Diffusion is as easy as typing in a thread of words. You can even create an image in the style of an artist whose work was scraped.

Artists have since begun sharing tools and resources for determining whether their work was scraped as part a dataset used to train Midjourney and Stable Diffusion.

Whether or not AI art tools violate copyright law can be difficult to determine. Images within these massive databases, that these AI tools “learn” from, may be protected by fair use doctrine. As The Verge reported, it’s a complicated matter of evaluating both the “inputs” (the images scraped from these databases) and the “outputs” (the images that the AI art generators create), for copyright law violations.

In response to the suit, a Stability AI spokesperson told Polygon, “Please note that we take these matters seriously. Anyone that believes that this isn’t fair use does not understand the technology and misunderstands the law.”

Polygon has reached out to Midjourney, DeviantArt, and Matthew Butterick and will update this story when they respond.