The U.S. Supreme Court's decision in Chevron v. NRDC (1984) is a longstanding source of controversy. Some proponents of the doctrine argue that it facilitates our Constitution's separation of powers. This deference doctrine puts administrative agencies, under the control of our democratically elected president, ahead of unelected judges when interpreting ambiguous statutes to implement policy. Others, including Supreme Court Justice Elena Kagan, endorse broad agency delegation because "members of Congress often don't know enough—and know they don't know enough—to regulate sensibly on an issue."