Tab,
There are a couple of court cases that do find that the 2nd Amendment pertains to a Individual Right.
1st Case - I'm sure you have heard of the case now known as Heller vs. D.C? A local court found that that the DC gun ban was unconstitutional because it violated the 2nd Amendments protection of an Individual Right to bear amrs....
2nd case - DC appealed the case above and an appeals court upheld the decision.
On another point, any contract that violates the law is invalid. Indentured Servitude, for example, is illegal no mater how many times the Indentured Person signs on the dotted line.
On another point, I actually agree with your view of the rights of property owners. A business owner should be able to make decisions about how to run their business. If they think not hiring Blacks or serving Blacks or folks who carry guns is a good business decision, they should be free to do so.
They can post all the signs they want about their exclusion policies and ask anyone they want to leave the premise. However, all their postings of their preferences does not make it law.
If someone enters the establishment the owner needs to ask them to leave and if they refuse, they are guilty of trespassing, but guilty of no crime before that (I know local laws say differently, but they are as wrong as the laws that prohibit the property owner from asking those he wishes to leave).
So, if the owner cannot tell that the customer is Black or Irish or carrying a gun or had fish for lunch or whatever his personal criteria might be for service and does not ask the customer to leave, no crime has been committed.
In this same vein, an employer should be able to say you cannot carry on their property and terminate you if they find you carrying. However, there should be no violation of law involved.
Now, the employer should not be able to restrict you from keeping a firearm locked in your personal vehicle, which should be considered an extension of your home. To allow the employer to do so would then extend their restriction beyond their personal property.
Please note that I am in no way a legal expert or in the legal profession. This is just my view of what is correct so that each partiy's Rights are protected.