> I guess the problem is there's no way of knowing that? Is there a Proof of Work for code review?

In a live setting, you could ask the submitter to explain various parts of the code. Async, that doesn’t work, because presumably someone who used AI without disclosing that would do the same for the explanation.

Based on interviews I've run, people who use AI heavily have no problem also using it during a live conversation to do their thinking for them there, too.