I've already had to have the "I'm sorry but this is the end of our customer/business relationship." conversation with one store owner over one of these. I anticipate more. You have the right to request people not carry a weapon on your property, however any time you run a business open to the public, you are also creating a place of public gathering, and if you demand that individuals disarm themselves in order to enter, and then do not provide some measure of security to compensate for their disarmament, then you are creating a hazard to all those who enter your place of business.
"Use more gun." -The Engineer- (Team Fortress 2)