Rep. Samuel Sitgreaves observed on April 19, 1798, that “at a time when we may very shortly be involved in war [with France], there are an immense number of French citizens in our country.” The Federalist-controlled Fifth Congress enacted four controversial statutes to guard against the perceived peril of French émigres and French sympathizers dwelling in the United States at a time when the two nations might soon be at war.
One of the so-called Alien and Sedition Acts was “An Act respecting Alien Enemies,” or the Alien Enemies Act, passed on July 6, 1798. It said that whenever there was a declared war between the United States and another country, or if the United States was invaded or threatened with invasion by another nation, natives and subjects of the hostile nation who hadn’t been naturalized in America were liable to be apprehended and deported as alien enemies in a manner directed by a presidential proclamation. (The Naturalization Act of June 18, 1798 had made it much more difficult to obtain naturalization, increasing the “probationary” U.S.-residence period from five to fourteen years.) The Alien Enemies Act didn’t have a sunset provision, so it’s still on the books.
Here’s a marked-up printed version of the bill that became the Alien Enemies Act: