David Janes yesterday summarized the Arar case in a list of hard and relevant questions, and Chris Lawrence today condenses his thoughts as follows:

I honestly don’t know what to make of all of this. I have a sneaking suspicion that elements of the Canadian intelligence apparatus were trying to get the U.S. to do some of their dirty work for them, because the Canadian government would never let them get away with it on their own, but there’s also the distinct possibility that U.S. authorities were freelancing. It’s all deeply weird.

No one really knows, but I think Chris's summary is pretty accurate.