Off-Topic :
Fairfax Underground
Welcome to Fairfax Underground, a project site designed to improve communication among residents of Fairfax County, VA. Feel free to post anything Northern Virginia residents would find interesting.
Gendarmeries are typically a branch of the nation's military and act as law enforcement for civilian populations. As someone already pointed out, the Posse Comitatus prohibits the military of the United States as acting as such. This doesn't apply to the National Guard when it is under state authority...but when Guardsmen are called up to Federal service, the Posse Comitatus applies.