Understandably, this has always a point of contention.
I carrry concealed, either on my person or in my car, in Indiana daily. The subject of weaponry in private vehicles on other people's property is a tough nut to crack, indeed.
However, If your weapon is in a vehicle and it's on my property, your weapon is on my property. As the property owner, I should have sole discretion as to how my property is used. If I start letting The State determine the rules of use for my property, they will ultimately claim that property.
Where do you carry a weapon, then? If you carry it on your person anywhere except public roads/places or your own home, then you are being hypocritical.
The state can claim your property anyway ( eminent domain ). I guess these laws and stipulations are moot if you work in a Post Office .