I was coming in here thinking it was because of his speeding and then was going to reply that they need to just take away his license already.
Though this sounds like it's the paparazzis fault this time. The paparazzi were being stupid and not getting out of the way of a moving vehicle just to get a shot so they can make money. If they are surrounding the guy it's hard to back up or go forward without actually hitting someone.
Although, I feel Justin could have fixed the situation. He could have called police to bring an officer or two out so they help make a path for him to leave so no one would get hurt.