Law 15: What constitutes “from behind” the head? All of the ball behind all of head? center of the ball behind all of the head? center of the ball behind center of the head?
USSF answer (June 7, 2010):
While some particularly limber people may be able to position the entire ball behind their head, the rest of us are not that well enabled. The “from behind and over the head” refers to the hands, the means of delivering the ball. The hands must be positioned behind some portion of the back and top of the head before the ball is delivered.
A gentle reminder to all referees (and coaches and players and spectators) who read this: The referee should not go looking for offenses to call. Let the game flow if there is no clear — let us emphasize that, CLEAR — infringement that somehow affects the game.