There can exist no "private property" belonging to a corporation without corporate law allowing the creation of such corporations. I don't think it unreasonable to limit such "private property" such that employees and perhaps other law-abiding visitors cannot be disarmed.
There are plenty of limitations already on such "private property". Just try to design a parking lot for such "private property" without including parking spaces reserved for the disabled.
In Colorado, we assert the castle doctrine where a property owner has the right to defend their property and as such, have the right to say who can come on their property and restrict their activities once they are on the private property.