(Reuters) -A federal appeals court ruled on Wednesday that U.S. President Donald Trump's executive order curtailing automatic birthright citizenship is unconstitutional and blocked its enforcement nationwide. The 2-1 decision by the San Francisco-based 9th U.S. Circuit Court of Appeals marked the first time an appeals court has assessed the legality of Trump's order since the U.S. Supreme Court in June curbed the power of lower court judges to enjoin that and other federal policies on a nationwide basis. (Reporting by Nate Raymond in Boston; Editing by Jamie Freed)