Yes. The described action is illegal. It is unsporting for a guard to take a position behind a post player, or to take a position facing an opponent, or to take a position with his/her back to the ball and facing the opponent and then in either case, wave or hold the hands in front of the opponent’s eyes so that the opponent cannot see. Holding or waving hands near the eye for the ostensible purpose of obstructing an opponent’s vision is unsporting.