The case raises questions about the Trump administration's adherence to limits set by the Supreme Court. It carries the risk of a significant clash between the two coequal branches of government and potentially a full-blown constitutional crisis.

More than 50 Venezuelans were believed to be scheduled to be flown out of the country, presumably to El Salvador, from an immigration detention center in Anson, Texas.

High court acts in an emergency appeal from the American Civil Liberties Union over removals under the Alien Enemies Act of 1798.