WASHINGTON (Reuters) -The U.S. Supreme Court on Monday announced its first formal code of conduct governing the ethical behavior of its nine justices, bowing to months of outside pressure over revelations of undisclosed luxury trips and hobnobbing with wealthy benefactors. It was adopted after a series of media reports detailing ethics questions concerning some Supreme Court members, in particular conservative Justice Clarence Thomas, even as Senate Democrats pursued long-shot legislation to mandate an ethics code for the nation's top judicial body. Unlike other members of the federal judiciary, the Supreme Court's life-tenured justices had long acted with no binding ethics code.