None, its just unwritten laws of the game. By textbook intepretation there should be MANY obstruction fouls every game. But it isn't enforced and I don't think there's a big desire to enforce it either.I have always wondered what rule allows defenders to aggressively block off attackers from the ball to win a goal kick? Clearly they also do not have possession as it was last touched by an attacker. How is that different from the OPs example?