The Trump administration said Sunday that hundreds of individuals were deported from the country after President Donald Trump invoked the Alien Enemies Act, a sweeping wartime authority which has been used only three times before,

President Trump says he’s using the 227-year-old law to crack down on Venezuela’s Tren de Aragua gang. The move is already facing a legal challenge. Here’s a look at key questions and answers about the Alien Enemies Act.