The president’s invocation of the wartime law enacted in 1798 was quickly blocked by a federal judge. It had only been used three times before in U.S. history.

In 1798, with the U.S. preparing for what it believed would be a war with France, Congress passed a series of laws that increased the federal government’s reach. The Alien Enemies Act was created to give the president wide powers to imprison and deport noncitizens in time of war.

After a federal judge temporarily blocked an effort by President Donald Trump to use the Alien Enemies Act of 1798, the Trump administration deported hundreds of immigrants to El Salvador alleging they are members of a Venezuelan gang.