Canada-US Civil Assistance Plan (CAP)

As we know, The Posse Comitatis Act prevents the US military from conducting domestic law enforcement operations in the US. How about if we requested assistance from a foreign military? Say, Canada? What would prevent a foreign military from conducting law enforcement in this country? Are they subject to the Posse Comitatus Act?

The Rules of Engagement (ROE) portion on pg 5 states Canadians can use "up to deadly force" in self-defense.
http://www.northcom.mil/News/2008/CAP%20-%20For%20Public%20P...

Check out this "Tri-Command Framework" doc, pages 24-26 outline AORs. The US and Mexico are in Canada's AOR?
http://www.northcom.mil/News/Signed%20Framework%20Sep%2009.pdf

Another tidbit:
REMARKS BY GENERAL GENE RENUART (NORTHCOM/NATO) at the 2009 Canadian-American Border Trade Alliance

the threats to North America. Prime Minister Harper stated that there is really no such thing as a threat to the national security of the United States which does not represent a direct threat to Canada. And that's an important statement, because today those threats can come in a variety of ways. We might call H1N1 virus a threat to our two nations, and we're partnering today across our borders to ensure that we provide the right protection to our citizens, the right preventative measures to ensure that this virus, this flu doesn't expand into something of a pandemic nature, and I think both nations have shared and worked collaboratively very well to try and ensure that we don't see that kind of growth and change. But there's a lot that we don't know about flus like this, and I think if we continue to work collaboratively we'll ensure that we're better prepared if and when the next one occurs. Certainly, a problem like the H1N1 virus can affect trade. And we already see that with the long lines crossing the border from Mexico into the United States. And we see that concern over how much freedom we allow in tourism. I was listening to CTV this morning, and there are some Canadians who are in hotels in strange places around the world right now, not able to leave until the quarantine process is over. By the way, they looked like they were having a pretty good time. So they weren't under stress by any stretch of the imagination. But how we collaborate on things like that is important to the trade and the relationships between our two nations. If we are to be successful in the future, collaboration is the way to approach this. And I think this virus outbreak has shown that the two nations are increasingly collaborative in virtually everything we do.
http://www.northcom.mil/News/Transcripts/050509.html

I am not sure how exactly how to process this stuff, so i thought i would throw it up to the DP for further analysis/comments.