The act is a wartime authority that allows the president to detain and deport non-U.S. citizens from enemy countries.

Trump is expected to invoke the Alien Enemies Act as part of the efforts to carry out mass deportations, according to two U.S. officials familiar with the matter.

President Trump plans to invoke a centuries-old wartime authority to accelerate mass deportations of undocumented immigrants with little to no due process. Why it matters: Trump floated invoking the law on the campaign trail.