The line between alien and citizen has often been crossed before. In fact, two of the most shameful episodes of our nation’s history also had their provenance in measures initially targeted at non-citizens. The McCarthy era of the 1940s and 1950s, in which thousands of Americans were tarred with guilt by association, was simply an extension to citizens of a similar campaign using similar techniques against alien radicals in the first Red Scare thirty years earlier. The earlier Red Scare, which culminated in the arrests of thousands of aliens for their political associations during the Palmer Raids, was coordinated by a young J. Edgar Hoover, then in the Alien Radical division of the Justice Department. Hoover applied what he had learned in the first Red Scare to U.S. citizens during the second Red Scare, which targeted thousands of them.

The same pattern underlies the internment of U.S. citizens of Japanese descent during World War II. Since 1798, the Enemy Aliens Act has authorized the president during wartime to arrest, detain, deport, or otherwise restrict the freedom of anyone over fourteen years old who is a citizen of the country with which we are at war, without regard to any actual evidence of disloyalty, sabotage, or danger. The justification for that law, which the Supreme Court has upheld as constitutional, is that during wartime one can presume that citizens of the enemy country are loyal to their own country, not ours, and that there is insufficient time to identify those who are actually disloyal.

In World War II we simply extended that argument to U.S. citizens through the prism of race. The Army argued that persons of Japanese descent, even if they were technically American citizens because they were born here, remained for all practical purposes "enemy aliens," presumptively likely to be loyal to Japan.