Somehow I think that if you had employees sign a contract where they agreed that as a non-White Male employees they would be paid 20% less for the same work than White Male employees you would be facing right violation charges soon.
And since we cannot handle different rights in different ways, it would seem that violating an employee's 2nd Amendment Rights would need to be treated the same, even if they signed a contract allowing such infringement.
Many employers restrict firearms possession in private vehicles in company parking lots. This will negate your right to self protection on your way to and from work at least.
As far as legal goes, my shooting range is located so that I would have to drive through a half mile stretch of a city that had restrictions on having loaded firearms. The drive through this city took me past a 5 story clock/bell tower and I often asked my self what would I do if, as I passed the tower, a whacko started shooting folks from atop the tower.
Since stopping this act would be an easy shot with the skill I have with the rifles I carried, I somehow don't think I would have been able to say...Illegal is Illegal...I'll just drink my coffee till the traffic clears...