Even before generative AI was an issue, in the US you couldn't just tell a court "this is a photo, therefore it is evidence". There had to be witnesses would could testify about how that photo was produced, and the other side could cross-examine.

But yes, you're already seeing politicians caught doing or saying embarrassing things claiming it's all a deepfake, but in most prominent cases of this there were lots of witnesses who can confirm that yes, they did say that.