President Donald Trump has invoked the Alien Enemies Act, a tool that grants the president sweeping power to imprison and deport non-citizens in time of war, to target alleged members of a Venezuelan gang.

A U.S. federal judge asked the Trump administration to explain how it failed to act on its court order to halt the deportation of hundreds of Venezuelan migrants, including alleged gang members, escalating the confrontation between the President and the federal judiciary.

An extraordinary legal showdown took place last weekend over President Donald Trump’s invocation of an 18th century wartime act to deport hundreds of immigrants, most of them Venezuelans, to a prison in El Salvador.