Mike my guess is it is pretty unlikely you would be stopped where you are but on a Canadian BB I have heard reports (this IS second hand so take it as you will) of customs agents cruising the local parking lots of gun/sporting goods shops etc and then stopping cars as they approached the border. This was for Canadians coming back into Ontario.

If you go onto Canadian Gunnutz, there is an extensive legal section with full explanations of all of this stuff if you search the threads.

The world cries out for such: he is needed & needed badly- the man who can carry a message to Garcia