Isn't it an underlying principle? It's meant to prevent detainment without proof of guilt. Otherwise, people could be held indefinitely for no reason. Now obviously there is a gray area between "hey we can't hold on to anyone until the courts say so" and "I don't like the look of that guy, lets put him in jail." But I don't think it's unfair to argue that handcuffing and pointing a weapon at someone who has not posed a threat and is only under suspicion (unreasonably in my opinion) of stealing a laptop is an over reaction and in conflict with that principle. To me, the level of detainment is not commensurate with what is reasonably required in order to investigate or protect the public interest.