My second son was actually refused entry into Canada once. (This was quite a few years ago.. before he got married and settled down.) Here's what happened..
He and his friend spent quite a few weeks in the Summer helping friend's dad with his seasonal firework business. Well, one night they decided to take a road trip, which included going to Canada. It's not that far when you live in Michigan. (Laugh.)
The problem occurred because they tried to cross the border with a van full of fireworks! Apparently the Canadian border patrol didn't want explosives being brought into their country. Go figure.
Son and friend were ushered into a holding room while the van was searched. They were denied entry and told to turn around and go home. Which they did.
You can play this at Hump Day Humor.