Is Missouri an 'employment at will' state? If so, they can change the 'employee manual' all they want without notifying you. My personal advice would be to say 'Ok I won't carry at work anymore' and leave your weapon in the car for your protection to & from work, just don't tell them. I know here in Texas, your car is an extention of your home; someone entering it w/o premission is tresspassing. If they take anyting out, it's thieft; theift of a firearm is a felony! I would also, if possible, park your vehicle off their property. I had to do that with a former employer; my car and anything in it were then not subject to their rules. Good luck amigo!