Good question.
I don't know. That's the main issue with photo privacy, other people tagging you in their pics.
I guess fb notifies you and you can go back and untag yourself. That's what I used to do.
I don't really care that the person tagged me in the photo. I just think it's funny that a person could tag me in a photo and then look at my profile and see it say that I'm not tagged in any photos.