Earlier quoted context omitted.
I agree with "I'm fairly certain this will defeat 99.9% of malicious users". Also, note that C2PA should have something like Level 3 as well: "The image is mathematically proven to have come from the physical camera sensor." It's somehow difficult to achieve this, but it's possible (although the attacks will always be possible of course).
Difficult and also solves nothing, since you can just point the camera at a screen.
The screen is doing all kinds of crazy things that are not apparent to your eyes, but that show up clearly on camera.