This is the narrow gap that I was speaking about.
The way Bill C-17 is crafted for preventive detention allows law enforcement, when they have reasonable grounds to believe there is going to be a terrorist attack, to detain persons if they have reasonable suspicion to believe detaining them will forestall that terrorism attack. Conventional criminal law usually allows a person to be detained only when there are reasonable grounds, so the virtue from a law enforcement perspective is that it lowers the threshold for when someone can be detained for this finite period of time.
In my paper I speculate on when a situation may arise in which law enforcement believes there might be an imminent terrorist attack but may not have enough concrete evidence to single out an individual and to rise to the level of reasonable grounds to detain that person. They just have a suspicion about that person.