Article II. Section 2. “He (the President) shall have power, by and with the advice and consent of the Senate, to make treaties, provided two thirds of the Senators present concur; and he shall nominate, and by and with the advice and consent of the Senate, shall appoint ambassadors, other public ministers and consults, judges of the Supreme Court, and all other officers of the United States, whose appointments are not herein provided for, and which shall be established by law; but the Congress may by law vest the appointment of such inferior officers, as they think proper, in the President alone, in the courts of law, or in the heads of departments.”
Any claim of authority by an executive actor must be founded in law. Article VI of the Constitution recognizes three sources of federal law: the Constitution, statutes, and treaties. The only executive actor in whom the Constitution directly vests legal authority is the President. Several of the President’s specific constitutional powers are almost certainly not subject to delegation. It is highly doubtful whether anyone but the President may sign a bill, veto a bill, issue a pardon, appoint an officer, or make a treaty, for example. It is also quite doubtful whether the President may delegate the authority, conveyed by the Vesting Clause of Article II, to oversee and direct the subordinates who perform the executive functions of government. In any event, I do not understand that the President claims to have delegated to anyone any of the powers vested in him by the Constitution, nor that any of this recent predecessors did so. As a result, in general any executive actor other than the President who claims legal authority must rest that claim on a statute.
One implication of this reasoning is that any member of the White House staff, whatever the official or unofficial title of that staff member, who does not have statutory authority does not have any legal power. A member of the White House staff who is referred to for descriptive purposes as a Tsar but who has no statutory authority cannot take actions with any legal effect.
The Appointments Clause of Article II provides that officers of the United States are to be appointed by the President with the advice and consent of the
Senate, but that if Congress so prescribes inferior officers may be appointed by the President alone, the heads of departments, or the courts of law.
So, if these folks are going to have any significant authority, as opposed to ministerial employee or inferior officer, it would seem we need a statute granting that authority.
Looking at a concrete example -- Why does President Obama need a “Special Envoy for Climate Change”? The Climate Czar reports to Secretary of State Hillary Clinton, but we already have the Environmental Protection Agency and the National Oceanic and Atmospheric Administration that includes the National Weather Service. What exactly does the Climate Czar do and why? If he has no authority, what are we paying him for? We have an energy and environment czar who is reportedly coordinating policy in the same area as the “climate change” czar despite the fact that we have both a Department of Energy and an Environmental Protection Agency. Then there is the "green jobs" czar. And, what about the "pay czar?" Who was that? Feinberg? He had authority to set the pay scale for executives at companies getting federal aid - but, where did he get that authority from?
Early on in the Obama administration Senator Byrd wrote to Obama these appointments violate both the constitutional system of checks and balances and the constitutional separation of powers, and he wrote that it was an attempt to evade congressional oversight.