Do I remember wrong, or didn't they dig up Dewey from some prison in an earlier episode? And I don't think this series is exactly one of those where one man matters that much. One bullet would be enough to stop Dewey. It just looks like the leaders of the world don't have a better plan to get things to the state they like other than Dewey's way. Obviously he has been given a lot of authority. And so it's also good to remember the kids themselves don't actually have any authority (as they have pretty much told themselves): Take Dewey away, and the military would probably kick the annoying kids out of the aircrafts (without parachutes).