Hair protocol in the kitchen

A hat in the kitchen is a must in my opinion. What happens when you hire a person and their hair poses a potential problem? I recently started interviewing cooks and a lot of them had the *gulp* top knot or man bun and tell me they worked in places where they didnt have to wear anything on their head. In my kitchen, there are no exceptions and I think if you're in this industry for the long haul, long hair has no place but can I actually exclude someone based on this alone or go as far as to ask them to cut it? I'm not trying to be a tyrant but finding hair in food is probably my biggest pet peeve when it comes to avoidable kitchen mistakes.