Another quotation from Garrard Glen in 'The Army and the Law' (1918) citing the US Supreme Court:

"In war," says our Supreme Court, "all residents of enemy country are enemies.'' And in another case that Court has declared that "it is ever a presumption that inhabitants of an enemy's territory are enemies, even though they are not participants in the war, though they are subjects of neutral States, or even subjects or citizens of the government prosecuting the war against the State within which they reside.”