Getty Images has filed a lawsuit against Stability AI, alleging the company trained its Stable Diffusion art generator using 12 million images from the Getty database without permission or compensation. The stock photography firm claims Stability AI engaged in “brazen infringement” of Getty Images’ intellectual property “on a staggering scale.” The suit was filed in the U.S. District Court in Delaware. Last month, a trio of artists seeking federal class action status also sued Stability AI, along with AI startup Midjourney and the Wix-owned DeviantArt, which uses Stable Diffusion for its own DreamUp generative imager.

The San Francisco-based trio claims violations of the Millennium Copyright Act and right to publicity among other causes in a 46-page complaint that includes examples of how the plaintiffs feel AI infringes on their art.

Generally speaking, the argument in defense of model-trained AI art generators is that human artists also view and take inspiration from existing images, sometimes going so far as to copy works in an effort to learn their craft, which is not considered illegal. Digital imprinting as part of model training, however, is a new type of legal challenge with no direct precedent.

The copyright infringement arguments of both lawsuits will center on interpretations of the U.S. fair use doctrine, which permits unlicensed use of copyrighted material under certain circumstances.

“The concept of ‘transformative use’ is also likely to be an important factor,” reports The Verge, which identifies as key the question of whether Stable Diffusion’s output differs substantially from its training data. “Recent research has found that the software memorizes some of its training images and can reproduce them almost exactly, though this only happens in a very small number of cases.”

In January, Getty initiated legal action against Stability AI in the UK, where the artificial intelligence startup is based. Aaron Moss, a copyright lawyer at Greenberg Glusker who published Getty’s U.S. complaint on his Copyright Lately blog, says the photo agency has focused on “the input stage ingestion of copyrighted images to train the data” and “the fact it wasn’t paid for the use of its images.”

Also mitigating in Getty’s favor, according to The Verge, is the fact that the company has previously entered into licensing arrangements with other AI firms for images and metadata used to train models, “underscoring the fact that Stability AI willfully scraped its images without permission.”

“Getty is in a slightly different position than artists” because it says its being harmed not just because its images are being scraped, “but also because of all the detailed descriptions and metadata that Getty collects,” writes Ars Technica, noting that “Stability AI can use that data to better respond to user prompts, basically using all of Getty’s input to unfairly compete with the image provider.”