Suppose an AI art model was trained exclusively on Mr. X's artwork. Suppose Mr. X managed to prove that the model was only capable of producing derivative works. He would then own the copyright to all the art produced by this model. But would Mr. X also own the AI model?
Now, let's take this question one step further. Suppose an AI art model was trained on art generated by millions of different artists. And suppose these artists managed to prove that the model was only capable of producing derivative works of at least one of these artists. Would the model then become public domain?
Whether AI-generated art is derivative has already been hotly debated, and that is not the point of my question. If the artwork is proven to be derivative, who owns the model?