If you work for a corporation then let the corporation answer this problem for you. Report the problem to whoever is above you. Call the headquarters. You won't need state or federal guidelines, just corporate ones. If there is a regional corporate manager, call them. If you can go directly to the head office, call them.
I would be surprised if the corporate office doesn't have a policy but if they do not, all you need to do is have the whole thing on corporate record to document your efforts. When they come up with a policy, you can show you tried so no one can call you on allowing it.
In the event there is no policy and no corporate guidelines, let it go. You have to pick your battles and this one may not be worth the trouble if the employee is otherwise a good employee. If they aren't a good employee, this issue won't matter as they won't last anyway.
I would also take into consideration the attitude of the other employees. Are they for or against and if so why? If the smoker is the odd one out, feeling ostracized can be a big attitude adjustment. If the staff is for it, what reasons do they have?
I'm curious as to why this employee is pushing back so hard on this issue and what that represents about the overall work atmosphere or their personal attitude.