Chief Justice John Roberts wrote for a 5-4 majority. He was joined by Associate Justice Brett Kavanaugh and the court's liberals. Associate Justices Samuel Alito, Neil Gorsuch, Clarence Thomas and Amy Coney Barrett dissented.
In the final opinion handed down in the 2021-2022 term, a rare win at the court for President Joe Biden, Roberts said that the lower court's ruling against the administration "imposed a significant burden upon the executive’s ability to conduct diplomatic relations with Mexico." That's because, Roberts noted, the United States cannot unilaterally return migrants who are from Central America to Mexico. Those returns must be negotiated with Mexican officials.