Earlier quoted context omitted.
The fact of the matter is they don't. What they want to do is go fishing through your papers and they cynically use this catch all excuse when challenged. In Canada it isn't legal to arbitrarily search people even at the border. Reasonable cause is necessary: http://laws-lois.justice.gc.ca/eng/acts/C-52.6/page-64.html#... There is both plenty of incentive and no consequences for conducting unlawful searches.
>The fact of the matter is they don't Do you have any references for that? From what I can see on programmes like Border Security, they do catch a lot of people this way, and they do always have reasonable grounds for the search. Also, how does that law allow random searches at airports (which are presumably legal)? Is there another law which permits those?
I can't stand those shows, I have to change the channel, they literally make me angry. Thinking that there are people out there who actually fall for it makes it worse.