President Donald Trump has invoked a rarely used 1798 law that gives a president immense powers to arrest and deport noncitizens in a time of war.

A federal judge didn't have the authority to order the Trump administration to broker the return of a Maryland man who was mistakenly deported from the U.S. to a notorious El Salvador prison, government attorneys argued Saturday as they urged an appeals court to suspend the ruling.

There is a "fair likelihood" the Trump administration violated a court order temporarily blocking the deportation of alleged Venezuelan gang members under a rarely invoked 18th-century law, a U.S. judge said on Thursday.