8 CFR 331.1: Definitions.

As used in this part:

Alien enemy means any person who is a native, citizen, subject or denizen of any country, state or sovereignty with which the United States is at war, for as long as the United States remains at war, as determined by proclamation of the President or resolution of Congress.

Denizen includes, but is not limited to, any person who has been admitted to residence and is entitled to certain rights in a country other than the one of the person's nationality. A person holding a status in another country equivalent to that of a lawful permanent resident in the United States would be considered to be a denizen.