I will make a quick comment, so that the others have time to answer as well.
This is what is going to happen in practice. Even though such individuals were not brought before a court, I am sure this has happened. CSIS agents go to people's houses, tell them that if they don't answer their questions about the next door neighbour, if they don't rat on their neighbour, that they have the power, with the police, to detain them for 72 hours and then compel them to come before a judge who will force them to answer all their questions.
This is a form of intimidation that will work, even if it yields only poor results in their investigations. Unfortunately, it will be used for profiling because of the definition of terrorist activity.
I'll stop now and let my colleagues answer.