President Donald Trump used wartime authority to deport nearly 240 alleged Latin American gang members to a mega-prison in El Salvador over the weekend. A federal judge unsuccessfully sought to block the administration’s actions,

(CNN) — The Trump administration has sparked controversy with its move Sunday to deport 261 people, some of whom it alleges are members of the Venezuelan gang Tren de Aragua, to an infamous maximum-security prison in El Salvador.

The Trump administration has invoked a 227-year-old law, the Alien Enemies Act, to target Tren de Aragua, a gang with its roots in the prisons of Venezuela. Who are they and how wide is their reach?