George Sutherland, Humphrey's Executor v. United States…
“ The authority of Congress, in creating quasi legislative or quasi judicial agencies, to require them to act in discharge of their duties independently of executive control cannot well be doubted; and that authority includes, as an appropriate incident, power to fix the period during which they shall continue, and to forbid their removal except for cause in the meantime. For it is quite evident that one who holds his office only during the pleasure of another cannot be depended upon to maintain an attitude of independence against the latter's will. ”
