A federal judge late Saturday blocked President Donald Trump’s executive order invoking the Alien Enemies Act to deport migrants—even ordering the administration to turn around flights that had already departed—the latest in a string of court rulings against Trump and cost-cutting czar Elon Musk.

Administration officials said they expect the fight over using the wartime act to ultimately head to the Supreme Court.

Trump officials said the deportations don’t violate a judge’s order barring use of the Alien Enemies Act for removals -- but also questioned the order’s validity.