[Kalium]

If you assume that "Anyone could have been using that camera!" is a defense, you're absolutely correct.

It's perhaps worth considering that an authoritarian government might not trouble itself with such legal niceties. All they have to do is mandate that journalists with cameras register their keys, make possession of a camera with an unregistered key criminal, and track sales / border entries. China springs to mind as a country that might do such a thing.

Again, you're absolutely correct in asserting that anonymity of camera-user is important! It's just perhaps worth considering how linking hardware to images might undermine that in dangerous ways.