What is the Alien Enemies Act that Trump plans on using to deport migrants to Guantanamo Bay?

Multiple U.S. officials familiar with President Trump’s immigration plans say he will invoke a 227-year-old wartime law to authorize the deportation of some migrants as soon as Friday. This would include deportations to the U.S. Naval Base at Guantanamo Bay in Cuba. CBS News immigration and politics reporter Camilo Montoya-Galvez has more. Source