Canadian border story:
circa 1966 a youngish & certainly naive m657 attempted to visit Canada, driving to the Idaho/BC border crossing.
The nice young man there asked about firearms. Pondering whether he meant the Mk I Ruger buried in the trunk, casual inquiry prompted revealing all the sordid details of my attempted invasion of Canadian sovereignty. He agreed under the circumstance, since I hadn't actually penetrated deep into Canadian territory & didn't seem to be intent on some horrific subterfuge, I could box it up & mail it back to my home address down there in south Idaho.
Chagrined still a few days later returning thru the same small border check point, I was interrogated by a US guard. He advised of the dire consequences should they discover undeclared illicit items, especially firearms, among my possessions...which he proceeded to drag out of the trunk and expose to the ample sunlight along with my spare underwear carefully tucked away.
Not discovering any contraband I was waved back in to my Native Soil. I was struck by the difference at the time between the 2 approaches, almost a Good Border Guard/Bad Border Guard, although they were independent of each other.
So while I didn't mail-order any firearm, the 'ship it to yourself' was present at that time at least.