They are illegal to use and illegal to have (even if in the trunk of your car). They treat them like contraband.
A clip from a quick article I Googled:
''IF you drive into the Yukon territory,'' said Fred Jennex, Deputy Minister of Community and Transportation for the area, ''you better hide your radar detector very well.'' The Yukon is one of 7 Canadian provinces and territories - there are 12 in all - that ban the possession and use of radar detectors in automobiles. And the news is worse than just a fine; confiscation of radar detectors, which cost $100 to $400, is a likelihood for drivers who get caught using them. Quebec Province crushed and incinerated 10,000 radar detectors last year, according to officials there. Canadian rules apparently come as something of a shock to drivers from south of the border, since only two states - Connecticut and Virginia - and the District of Columbia ban them in the United States. etc... etc...