I would be careful with that one, unless something in the employee handbook mentions it.
When I was at Panera their policy said that employees are not allowed to possess firearms or other dangerous weapons. It made no mention to on the clock or off the clock, I called corporate HR and asked if I came in off of the clock, as a customer, would the rules still apply. They told me that because I was an employee and a "representative" of the company that I would not be allowed to carry to Panera, even off of the clock as a paying customer. Is this true, I dont know, but they can always fire you for anything since this is an at will state.