2018 International Rule Changes
10. THROW-IN RESUMPTION OF PLAY WHEN THE BALL HAS NOT LEFT THE FIELD
d.) If a player is on the wrong side of the line-up when the ball is thrown in, he may not make a play until he is behind a member of his own team. Should he make or attempt a play prior to being passed by a member of his own team, a penalty shall be awarded.
e.) During the throw-in, the right of way will be established when the ball leaves the line-up. Until such time, players may play the ball from any direction or angle providing they do so without creating danger or a risk of danger to themselves, other players or horses.