President Donald Trump recently invoked the Alien Enemies Act of 1798 to deport Venezuelan migrants, stirring controversy and legal challenges. The act designated the Venezuelan gang Tren de Aragua as a Foreign Terrorist Organization.

The law, which gives the president sweeping powers over non-citizens, was part of a set of statutes that emerged during the tenuous period following the Revolutionary War.

President Trump invoked the Alien Enemies Act of 1798 against Tren de Aragua members, provoking a legal fight. Here's what to know about the controversial law, which was last used during World War II.