Starwatcher,
Pepper spray if labeled for animal protection is legal to carry across the border.

I once had a border guard ask me if I had pepper spray and when I told her I had bear spray she told me I would be unable to enter until I got rid of it. I pulled in to turn around and other border guards were asking me what I was doing. I told them and they all looked at each other, wanted to know who gave me the instructions and then waved me through, bear spray and all.

It's not 100%. I once watched a video on regular TV where a guy maced a black bear 3 separate times point blank in the face. Each time the bear paused, wiped its face and continued the pursuit. Fortunately the guy was close to his car or else he would of been toast.

I keep it in the tent at night but personally believe it would be of limited use in a confined area and would likely render you incapacitated. Don't spray into the wind (Duh). For me it is a last resort. I would basically let the bear look around unless he shows interest in me personally and then I would be quick to react. The longer you wait the more confident they become.