Most Helpful Guy
If he's stopping you it's because he was told before hand what to allow and not allow. The celebrity won't deny you themselves because then they'll look like a jerk so they have the bodyguard do it. If he's stopping you from getting a picture the celebrity did not want the picture to happen.
Most Helpful Girl
Obviously all in all it's the celebrity's or their manager's choice - but it all depends on the situation.
If it's a huge uncontrollable crowd the body guard is going to dismiss everyone because he can't control that huge crowd so he's worried solely on the celebrity's well being, while if there's a few people and the celebrity is in a good mood - they'll tell the guard to step down and that it's okay.