Getty Images, which licenses millions of news, sports and stock photographs, asked the Court of Appeal in London on Wednesday, November 11, to revive its copyright case against Stability AI, the British company behind the image generator Stable Diffusion. Getty says Stability used millions of its pictures without permission to teach the program how to make images, work it says was done in the United States. Last November, a High Court judge ruled largely for Stability. Because the finished program does not keep copies of the photographs it learned from, she found, it is not an illegal copy under British law. Getty won only on limited trademark points involving older versions.

The two-day appeal turns on a narrow question with wide reach: can software trained abroad count as an unlawful copy once it is brought into Britain, even if it holds none of the original pictures? Getty’s lawyer told the judges that Stability valued its collection for training but does not think it should have to pay for it. Stability argues that the images were downloaded and stored in data centers outside the country, so British copyright law does not apply. The BPI, which represents Britain’s record labels, has joined the case on Getty’s side. If Stability wins again, photographers, musicians and writers will find it hard to use British courts against AI companies that train their systems in other countries.