If, as I alluded to, you and the SCOTUS (and other courts) interpret AI art as similar enough to humans where the 'training' process is analogous to a human looking at art and learning how to create good art (or even copy another artist's style), then the license you apply to art does not matter, because it'd just be "learning" about how art works, and not any actual usage of the original work. In this case the AI would be considered a human for the purposes of copyright infringement, where it would infringe on the original work if it recited or recreated any single work from memory without any substantial changes to turn it into either a parody (fair use) or its own work separate from the images it has learned from, even if it mimics the art style of any single artist (since artists can't copyright their styles).

I think you’d consider those responsible for the model to be humans, the model to be a machine, and all outputs to be derivative works of the training set with the humans holding culpability.

Not as far as I know. There needs to be one, and internet-scrapers need to be able to be sued for ludicrous amounts of money if they violate it, IMHO. Training AI models feels way outside the scope of what I think "fair use" should cover.

They do not currently operate on the basis of fair use. Operating as a human by looking at images and learning how to draw or paint is not 'fair use', it's a right given to you by either God or Mother Nature, so the legal basis for neural nets learning from other art is that it's learning like a human and creating new art from just knowing what art human think is good and optimizing its creation of art to mimic if not borrow the same qualities while still making something new.

As far as I know there are no religions or legal systems that posit that there are any rights inherently given to machines.

The rights are exercised by the humans building and operating the machines. You're saying the hammer doesn't have rights. Well, yeah, duh. It's the person holding it.

"so the legal basis for neural nets learning from other art is that it's learning like a human and creating new art from just knowing what art human think is good and optimizing its creation of art to mimic if not borrow the same qualities while still making something new" sure sounds like it's attributing the rights to the machine, not the person using it, to me.

Not for lack of trying though. https://transhumanist-party.org/tbr-3/

Also if you are going to say that the neural net has the same divinely-given right as humans then I feel you are also implying that the neural net has all the other rights of a human, and I think labor laws would have something to say about keeping a six-month-old idiot savant in a box and making them draw whatever random querents on the Internet asked for, 24/7.

Non-commercial internet scraping for model creation is explicitly legal in the EU; the result of a model trained on a billion images really has nothing to do with anyone in particular's art. Although the model would likely work pretty well without ever seeing any "art" images.