After an "extended course" the booze would have probably fallen within his personal exemption. The chances are good that if he'd declared them he may not have paid anything at all on the over exemption (if any) booze, depending on the quantity. And if the port is busy, well, then "welcome back to Canada, have a nice day."
As a skilled competitive shooter, I'll hazard a guess that he has probably traveled OUTCAN with firearms before. If so, that's a pretty glaring "admin error".
And if any of those magazines were over legal capacity, that’s not even close to a new rule. “Stuff got reclassified while I was OUTCAN” won’t go very far in that case.