President Trump is planning to invoke a wartime law known as the Alien Enemies Act of 1798 as soon as Friday to authorize the summary deportation of some migrants, including to Guantanamo Bay, escalating his government-wide immigration crackdown, multiple U.S. officials familiar with the plan told CBS News.
According to the Brennan Center for Justice, the President can invoke the act without a war declaration if a foreign government threatens or attempts an “invasion” or “predatory incursion” against US territory. Invasion in that context has historically been defined as large-scale attacks, while “predatory incursion” has been defined as small skirmishes. And it’s the latter that Trump is hinging his argument on by declaring that the gang he’s claiming to target is working on the orders of the Venezuelan government.
https://www.brennancenter.org/our-work/research-reports/alien-enemies-act-explained