I do not recommend anyone taking a weapon into any place where a gun is banned, in particular a court house or cop shop.
But other places such as the Post Office it could be easily done simply by having the weapon well concealed. There is just no way a gun could be detected in most places.
I personally do not take a gun into a PO, but private commercial businesses that have a No Weapons sign on there doors I say to hell with it. I will take a concealed weapon into those places. It’s well concealed and no one will ever know I have one unless I pull it out and brandish it, and I’m not that stupid. If a criminal starts gun play in such a store I will retreat and get the hell out. The gun will come out only if I am directly threatened.
Certainly good advice.
But if the courts decide that the Post Office cannot ban guns, I guess I'd like to see the reasoning that says courts ARE allowed to ban guns. I understand why they would want to, but it's obvious infringement and why is that OK here but not there?