The Alien Enemies Act is an 18th-century wartime law that allows the U.S. government to detain and remove immigrants from the country during times of war or conflict, historically used to address perceived threats from foreign nationals.

The Supreme Court temporarily blocked the deportation because the detainees were at imminent risk of being removed without due process and lacked adequate notice or opportunity to challenge their removal, violating a recent court ruling.

The ACLU filed an emergency appeal highlighting that the Venezuelan detainees faced imminent deportation without proper legal process or translation of notices, prompting the Supreme Court to issue a temporary halt to the deportations.

Justices Clarence Thomas and Samuel Alito dissented, indicating a division among the Supreme Court justices on the legality and appropriateness of the government's actions under the Alien Enemies Act in this case.

The government claims authority under the Alien Enemies Act to swiftly remove immigrants believed to be members of the Tren de Aragua gang, regardless of their immigration status, citing national security concerns.