Unless the law has changed in the 16 years since I have been a cop........Probably Cause is "more likely than not, has committed, or intends to commit a crime, and the person(s) being detained is more likely than not, the one(s) who commited it".
The Tampa Bay Bucs have a pirate flag, and there are no shortage of people who display it on their vehicles. Pirates have a much longer history of crimes against humanity than IS, AQ, BH, AS, HQN, IJ, Hamas, ad naseum. Much longer than the few years IS has been a player at all. I'd also be curious as to the "extensive history and experience" IS has.......certain elements and individuals sure........but as an organization, they are still shitting in their diapers.