I'm sorry, Bob...this violates one of the most basic tenets of American law.If you are aware of those conditions and choose to accept them by making use of their property, then there is not and should not be any liability on the part of the owner.
You'll have to do better.
To your further example...
Well, of course you are...and you should be. [nice transition from private business to private residential property, btw]During the course of our visit we all become the victims of a home invasion, and all of us are injured. Am I to be held liable in a court of law?
It's no different than if your guest has a couple of beers, gets in an argument with another guest, gets pushed in your backyard pool and drowns.
Or is playing football in your front yard and is mowed down by your demented neighbor in her Volvo station wagon because she didn't like his curl route.
You...the property owner...are liable.
It's your property...you are liable. The only solution to your dilemma is to do your very best to attenuate that liability.
Posting a property against those who legally possess and bear arms isn't going to attenuate that liability; it will [and should] exacerbate it. IMO, and as others have noted, this is perpetrating a fraud...suggesting that anyone patronizing your business/govt. office [you name it] is somehow "safer" because you have established a zone free from "gun violence".
Frankly, I'm surprised that such a case hasn't been filed, tried and won already...it's textbook in its simplicity.
Picture this courtroom scene:
**********
The aggrieved widow's lawyer addresses you as the first defense witness in her $100 million wrongful death civil suit: "So, Mr. Locke...is it true that you posted your property to deny the legal carrying of a firearm onto your business premises?"
Mr. Locke: "Yes."
Lawyer: "And exactly what effect did you envision that would have on any criminals using *illegal* carry on your business premises, Mr. Locke?"
[deafening silence ensues]
"Your honor, would you instruct Mr. Locke to answer the question, please."
***********
To recap, the business owner either accepts such liability as a condition of operating a business or sells his property...either before or after his business fails.
And I'll ask my question again:
How, exactly [and please be specific], is this legislation supposed to threaten property rights?
I still don't see it.