Electric shock???

Some days when I'm riding the train the is a person that stand in between the doors so they can't close. Even when the metro operator say please release the doors they don't. I am not talking about the people who run through the doors trying to catch the train. But those people who just hold the doors for countless others who are walking casually like the train is waiting on them. So I think that the operator should be able to push a button and send a nice electric shock into the door holders. Just a thought.