"The agreements also allow American customs agents to carry weapons within Canada, question people, and detain, but not arrest, them.".

Possession of loaded weapons by "security" defacto implies their use. So clearly it's OK for the American agents to shoot Canadians in Canada.

Wow, just wow! 

What are we doing for god's sake, allowing this? The Americans, the British, the Chinese almost any major power would never agree to this kind of loss of sovereignty. Are we such a small frightened country, that we can't even manage (or be trusted) to look after our own borders?