Boasberg found in April there was probable cause to hold President Donald Trump's administration in criminal contempt of court.
Judges Gregory Katsas and Neomi Rao, both of whom were nominated by Trump in his first term in the White House, concurred with the unsigned majority opinion. Judge Cornelia Pillard, who was appointed by President Barack Obama, dissented.
Boasberg had accused Trump administration officials of rushing deportees out of the country under the Alien Enemies Act before they could challenge their removal in court and then willfully disregarding his order that planes already in the air should return to the United States.
The Republican administration has denied violating his order.