President Trump invoked the 1798 Alien Enemies Act on Mar. 15, 2025 to order the swift detention and deportation of Venezuelan migrants suspected of being members of Tren de Aragua, a Venezuelan prison gang. In his proclamation, Trump argued the gang was 'perpetrating, attempting, and threatening an invasion or predatory incursion against the territory of the United States' - the legal threshold for invoking this wartime authority. The Alien Enemies Act had only been used three times before - during the War of 1812, World War I, and World War II - and never outside the context of a war declared by Congress. Trump's invocation marked the first use of the law for immigration enforcement. The administration deported more than 260 migrants to El Salvador over that Mar. weekend, including 137 alleged gang members expelled under the Alien Enemies Act. A distinguishing feature was that instead of detaining designated 'alien enemies' within the U.S. or repatriating them to Venezuela, detainees were placed in a foreign country's maximum-security prison.