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.

The act is a sweeping wartime authority that allows noncitizens to be deported without being given the opportunity to go before an immigration or federal court judge.

The judge’s initial temporary restraining order blocked the Trump administration from deporting five Venezuelans.