Thanks for your replies. A batter hit his first homerun and in excitement to his helmet off rounding 3rd. Homeplate umpire called him out for removing his helmet during a live ball.
It is, in the sense that if he misses a bag he can be called out. While I can understand being excited, players should not remove their helmet until back in the dugout or to hand it to a coach after a 3rd out if someone picked him up.
It is kind of like a football player not taking his helmet off until get to the sidelines.
I agree Jay, it is a little much. I think a strong warning would have sufficed. It is different than a player getting out running to first and ripping their helmet off in frustration and throwing it in the dugout.