The U.S. deported hundreds of immigrants after President Donald Trump invoked the Alien Enemies Act for the first time since World War II.

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.

The Alien Enemies Act of 1798 gives the president wartime powers to deport undocumented immigrants with little to no due process.