Back in the bad old days, when there was a border in NI, there were regular checks of cars going North / South.
One of the colleges in Dublin, had a student rifle club and they were on a trip to a competition in Comber.
Got through the border ok, made it to the match and had a good time.
On the way home, they were stopped again at the border. Got through fine. The soldiers wanted to check serial numbers against permits so they went through the collection.
When unloading the car back in college, they found an 'extra' gun in the boot.
About 30 minutes later, an NI car with some squaddies turned up, asking for their rifle back!