AUSA Theodore Cooperstein has this article in the Dartmouth Law Journal:

How should the United States deal with alien enemies during the ongoing Global War on Terror? The government's new policy to end the detention of combatants in Guantanamo Bay seems to offer only two choices: try alien enemies in the civilian criminal justice system or simply release them. Conveniently, the Alien Enemy Act of 1798 provides another alternative. This paper outlines the Act's history and explains its implications for America's options in dealing with alien enemies in the War on Terror.

1798? Another oldie but goodie.