Can we ban smoking on our company's property and not allow smoking during working hours (including lunch)?

You can certainly ban smoking on the company property, including offices, outdoor areas, and especially directly outside the entrances and exits-and prohibit "smoking breaks" during work hours (it always amazes me how office workers seem to feel entitled to take unlimited smoking breaks.). But if you are trying to prevent employees from smoking on their personal time away from company property, that's not possible because smoking is legal.