Turning him around would be the easy/common sense thing to do, but don't expect common sense to reign at any border crossing. For example:
I sometimes drive around with a quantity of drugs that are freely available in Canada over the counter (each pill contains 8 grams of codeine). I don't know what would happen to me if I tried to cross the US border with a couple of hundred of these and told the officer "I forgot they were in the car." I inspect my own car before I cross the border for a reason.
I understand you check you car, as do I. Like Jim Noble said, perhaps there’s too much missing still. It’s just a big sore spot for me living in Alberta that I can’t defend myself.
I mean, if I’m hiking or something along those lines, I carry a shotgun or rifle, but even then I can’t carry one of my handguns or carry concealed, it’s just plain stupid.