Would be very interesting to require generative AI companies to log their created images for that purpose, it isn't gonna eliminate self hosted alternative, but it can destroy any fake evidence faster
You can take a photograph of the image with an old Polaroid and, if the resolution is high enough, the watermark would still be there.
Let's now let's say your AI deepfake image is watermarked/hashed upon generation. Difficulty: Intermediate to hard. You might be able to get it done, but not without real effort, and removing all traces of the watermark without leaving artefacts might be so difficult as to be nearly impossible.
...So it doesn't eliminate the possibility of fakes, but it hugely raises the cost and effort bar. Only the most motivated would bother.
I tried some "AI watermark removers" on a Shutterstock image, and they did a pretty good job, but they left traces that would be obvious to any investigator.
The problem then is repeated compressing causing that to occur inadvertently