You have no inherent right to park this employer's parking lot. The owner is entitled to make his/her own rules, --
30 Melas
Most larger companies are required by local gov permits to provide company parking, and employees are required to use that parking rather than public spaces.
Our governments are charged by the constitution to defend our right to bear arms...not only in the public square, but wherever it is being unreasonably restricted.
Employees that are required to park their private property [vehicles] in company lots while working, cannot be reasonably compelled to give up their right to lock private property [guns] in those vehicles.
You may have a point if you can show me where an employee is compelled to park in the employer's lot. However,I know of no such ordinance in any place that I know of, so I'm extremely skeptical.