Gee, reminds me sort of Bakunin's invisible commitee...As someone familiar a little with an undeground state - we had one in the 2nd world war - there do exist secret courts of justice to prevent its members from going rouge. But of course the service of the state is greatly reduced, so it cover only the outmost important issues. The town or small entities govern themselves locally as before - like the Shire - but if needed the chosen local mayor might get "visited" by "strangers at night" wanting to persuade him away from e.g. accepting a Sauron's proposal. But nobody sees them in action on the levels below. And people high up in the hierarchy have some "red telephone" style ways to contact the "strangers" when needed, but never tell anybody below, only their successor.
But it probably also didn't come from nowhere , i guess there must have been incidents like that in history before, like during the french revolution. Sounds like something i would imagine the rangers to do...
Also sound like the plot for some cool rpg campaign.