Like jjk, I'd say it's wrong (unless the state of Indiana has a more stringent rule, or unless the team had already been warned about this previously in the game). (1.4.5-6 and Penalty)
1.4.5 ...It is mandatory for on-deck batter, batters, runners, retired runners, players/students in the coaches boxes as well as non-adult bat/ball shaggers to wear a batting helmet that meets the NOCSAE standard...
EXCEPTION: A violation by a non-adult bat/ball shagger shall result in a warning to the coach of the team and the individual. A subsequent violation may result in the individual not being allowed on the field.
1.4.6 ...A face mask may be attached to the helmet...
PENALTY: When an umpire observes anyone who is required to wear a batting helmet deliberately remove his batting helmet while in live-ball territory and the ball is alive (non-adult bat/ball shaggers required to wear batting helmets in live-ball area even if ball is dead), the umpire shall issue a warning to the coach of the involved team, unless the ball becomes dead without being touched by a fielder or, after being touched, goes directly to dead-ball area. A subsequent violation of the rule shall result in ejection.