Real time notifications here would solve a lot of issues...

Imagine Alice, an 18, 19yo girl, having a boyfriend, Bob, and since Bob is on a student exchange, she decides to send him a boob photo. Since alice is skinny, her boobs are on the smaller side.

Now imagine Alice hitting 'Send', and getting an automated message from whatever CSAM AI bot:

"Your message has not been sent, the system detected the breasts in the photo to be probably underage, the photo was forwarded to <your local police station> for manual review"

And half an hour later

"Detectives Rob Johnson, John Robson and Bob Bobson from police department XY, have done an extensive manual review of the photo of the breasts and have 2:1 decided that they're probably not underage, so the photo was sent to the intended destination. Than you, your friendly CSAM AI bot!"

I think you're probably wildly overoptimistic about the ratio of police officers to private nudes.

No government really wants to be fully enforcing all their own laws, just because it's way too expensive to hire that many cops. I think the closest anyone got was the Stasi, and they had a lot of "volunteers": https://en.wikipedia.org/wiki/Unofficial_collaborator#Other_...

I think a more realistic system would be hashing images and comparing them to known CSAM in some database.

I think Apple was going to implement something like this a few years ago before scrapping it.