One common proposal is that big companies should incorporate watermarks into the outputs of their AIs. For instance, this could involve taking an image and subtly changing many pixels in a way that's undetectable to the eye but detectable to a computer program.
A useful watermark for AI images would need two properties: It would need to continue to be detectable after an image is cropped, rotated, or edited in various ways (robustness). It couldn't be conspicuous like the watermark on stock image samples.