Who are Ferguson's 'Oath Keepers,' and why are they patrolling the city with guns?

On the one-year anniversary of Michael Brown's shooting death by police, tensions are once again simmering in Ferguson, Missouri. And the arrival of a militia group, known as the "Oath Keepers," threatens to add fuel to the fire in the St. Louis suburb.Founded by a former Army paratrooper and Yale instructor named Stewart Rhodes in 2009, the Oath Keepers's self-described mission is to "defend the Constitution." To that end, the group publishes a list of 10 "unconstitutional orders" which its members must pledge not to follow, including taking part in warrantless searches, detaining Americans or seizing citizens' weapons.The Oath Keepers came to Ferguson during last year's unrest and the group returned this week ostensibly to keep watch over protests commemorating the one-year anniversary of Brown's death.But the group's paramilitary style — members have been photographed perching on rooftops and outfitted with military fatigues and assault rifles — has created concern among local resi