If the paperwork isn't done exactly as CANADA CUSTOMS wants it done, they hold things up for any reason whatsoever.
That's one example I've heard my FLGS given. As Winnipeg is close enough to the border, them sometimes do a big pick-up and just drive it back rather than dealing with stupidity.
"Swords that are properly marked, no problem, but a tent with a typo and they're ON THE JOB!"