Not entirely, there are AI-driven photo analyzers that were created with this in mind. As an example site, Tumblr uses this to detect nudity and other unsavory media.

LoneTreeLeaf: Understood, but What do you think that costs in hardware / network provisioning, user experience friction when posting compliant material that still has to be checked, bandwidth, and service fees?

If it's going to be a small site I think the best way is to have videos be approved by admin first in settings but images would be harder. Maybe a mod that moderates file names. Sometimes rated R images have file names containing R rated words