AI is a tool, not a solution. If someone uses it to write code they don't understand and that is flawed, that should never pass code review.

If your AI generated code passes code review without any questions asked and without any hints that it's AI generated (or AI was used in some way), then it doesnt matter that it was used.

The person submitting the code is still responsible, and the reviewer is equally responsible. You typically have tests to make sure it behaved correctly, too.