Two opposing field players are going up for a header. If one of the players jumped up and over the opponent, knocking the opponent out of the way or to the ground, I’d be calling a foul.

What if the jumping player in the above scenario was a goalkeeper trying to reach a ball with her hands? Is the goalkeeper given any special allowances? I heard an instructor say “yes” and that fouls in this sort of situation are not called (as seen on TV), but it seems to me that the defender has just as much right to fairly challenge for the ball as the goalkeeper and to not be unfairly charged/pushed/struck.

(I indicated a game level of U13-19, but would the answer be different if we’re talking about pros?)

USSF answer (July 18, 2011):
What referees call and what referees SHOULD call are often two different things. The Interpretation of the Laws of the Game and Guidelines for Referees (p. 114) tells us: “All players have a right to their position on the field of play, being in the way of an opponent is not the same as moving into the way of an opponent.” In other words, no player, whether field player or goalkeeper, is allowed to go through any other player, whether field player or goalkeeper, to get to the ball.

Because the goalkeeper’s position is inherently dangerous (subject to hard challenges in the air, diving to the ground, lying on the ground, etc.), goalkeepers are allowed some leeway in doing their job. This means that they are permitted to reach over players and make some contact with the opponent, as long as it is not done carelessly, recklessly, or with excessive force.

Defenders or attackers, on the other hand, must take their chances as they find them. Jumping straight up or backing in to win the ball is not a foul unless the opponent is already in the air and moving to play the ball.