I think private property and the right to bear arms are both Constitutional rights. In this case, they clash.
Does Nancy Pelosi have the right to free speech in your living room, or in your gun shop? Does an Islamist cleric have the right to exercise his religion in your church? Does ACORN have freedom of assembly on your lawn, or in your business’ parking lot?
Do moonbats have the right to free speech on Free Republic?
I think the solution of giving employers the option of providing alternate ways for employees to be able to drive their guns to and from work balances the two fundamental rights.
No, private property rights do not extend to over-rule constitutional rights of others.
They should no more be allowed to refuse you keep a legal firearm in your car than to exclude people based upon race.