I think if it would of been a state to state violation, he would of surrendered the weapon, explained it was an honest mistake and after providing proof of ownership and legal registration, pay any fines and probably get his weapon back.

Some states recognize concealed weapons permits from other states, some don't. There are books maps that tell travelers that carry legal weapons what states reciprocate and those that don't.

I think considering he had the pot, it was a foreign country, he just was afraid to take the chance. A felony conviction, even if it didn't result in jail time, would probably cost him his liquor licenses in Atlanta.

You can bring long guns into Canada with certain restrictions on types and magazine capacity. You need to fill out forms. I know bringing a handgun in for hunting is a problem, I'm not sure if you can? I'm sure that for a fee and with proper paperwork you can bring your legally registered US weapons across the border, if say you were going to Alaska via Canada.

Yes, no state law supersedes International Law, as it should be.