But even then, if every pixel gets marked as ‘created by AI’, it would still be trivial to take real CSAM and run it through an image-to-image generator with denoising turned down to 0.05 and suddenly you have real CSAM that has been marked as ‘legal’ since it is technically AI generated.
Also, keep in mind that there are several open source projects out there where anyone who knows what they are doing could just strip out any protections that might be put in place.