He cannot expect the law to provide a penalty for a customer not following his rules when he has not informed the customer of what they are.
Nor can he expect the law to provide a penalty when those rules are burdensome to the patron.
For example, a business owner can't legally demand that someone in a wheelchair get up and walk around his store.
Nor can he legally demand than any women entering his store remove their tops after entering.
And likewise, he can not legally demand that lawfully armed citizens surrender their means to self-defense upon entry into his store.
If a business owner doesn't want to deal with gunowners, that is certainly his business. But it doesn't give him the right to expect there to be a law enforcing his irrational beliefs.