LEAVING THE FIELD TO PLAY THE BALL HELD IN THE CORNER

Question
ATR 3.9 states: “if a player . . . contesting for the ball passes over the touch line or the goal line without the ball to beat an opponent, he or she is not considered to have left the field of play without the permission of the referee. This player does not need the refereeā€™s permission to return to the field.”

Attacker A shields the ball at the corner flag from Defender B1, attempting to run down the time. Defender B2 leaves the field over the touch line and tackles the ball while re-entering the field from outside the touch line. Is this legal?

USSF answer (July 18, 2011):
You have neglected to cite the entire first paragraph Advice 3.9, which states unequivocally:

3.9 LEAVING THE FIELD IN THE COURSE OF PLAY
Players are normally expected to remain on the field while the ball is in play, leaving only to retrieve a ball or when ordered off by the referee. If a player accidentally passes over one of the boundary lines of the field of play or if a player in possession of or contesting for the ball passes over the touch line or the goal line without the ball to beat an opponent, he or she is not considered to have left the field of play without the permission of the referee. This player does not need the referee’s permission to return to the field.

In the scenario you lay out, the defender’s action was not accidental. It was, however, solely for the purpose of getting to the ball and lasted only long enough to get around an opponent. Accordingly, the defender’s momentary departure from the field was “in the course of play” and therefore entirely legal. In fact, the defender was only forced to take this action by the attacker who placed the ball and his body in such a configuration that the only way the defender could get to the ball was to leave the field.