ABSTRACT-The U.S. Constitution's separation of powers has its origins in the British idea of the desirability of a Mixed Regime where the King, the Lords, and the Commons all checked and balanced one another as the three great estates of the realm. Aristotle, Polybius, Cicero, St. Thomas Aquinas, and Machiavelli all argued that Mixed Regimes of the One, the Few, and the Many were the best forms of regimes in practice because they led to a system of checks and balances. The Enlightenment killed offthe Mixed Regime idea forever because hereditary office-holding by Kings and Lords became anathema. The result was the birth of a functional separation of legislative, executive, and judicial power as an alternative system of checks and balances to the Mixed Regime. For better or worse, however, in the United States, Congress laid claim to powers that the House of Lords and the House of Commons historically had in Britain, the President laid claim to powers the King historically had in Britain, and the Supreme Court has functioned in much the same way as did the Privy Council, the Court of Star Chamber, and the House of Lords. We think these deviations from a pure functional separation of powers are constitutionally problematic in light of the Vesting Clauses of Articles I, II, and III, which confer on Congress, the President, and the courts only the legislative, executive, and judicial power. The United States badly needs a rebirth of the functional separation of powers idea.
It is a privilege and an honor for us to write about the legacy of Justice John Paul Stevens with respect to the executive power specifically and the separation of powers more generally. Justice Stevens has had a huge impact on this subject, which all of us care about deeply. Justice Stevens was the author of two of the most momentous and consequential separation of powers opinions of the last thirty years: Chevron U.S.A. Inc. v. NRDC1 and Clinton v. City of New York.2 In the first case, Justice Stevens wrote a seminal opinion for the Court arguing for deference by courts to reasonable executive branch interpretations of law3-a view that he later wisely qualified in subsequent cases when some of his colleagues tried to take it too far.4 In the second case, Justice Stevens limited presidential power by holding unconstitutional a statute that purported to give the President a line item veto by delegating enormous impoundment powers to the President.5 The Chevron opinion and its progeny recognized that the President and his executive subordinates are often functionally lawmakers.6 The Clinton case sets outer limits on Congress's power to delegate its appropriations power to the President.7
Taken together, these two cases suggest that the very idea of the separation of powers is in a state of crisis today. Congress often passes sweeping delegations of legislative power to the Executive Branch,8 thereby placing courts in a quandary when they are called upon to review the legality of agency regulations and orders. Justice Stevens's opinion calling for judicial deference to reasonable executive branch interpretations of law in Chevron recognizes that quandary while his later opinions and votes limiting the scope of Chevron reflect the Justice's desire to preserve as much of the separation of powers as possible by allowing for judicial review.9 Congress also tried with the Line Item Veto Act to surrender part of the traditional legislative prerogative of the power of the purse to the President.10 Justice Stevens, writing for the Court, struck that particular delegation down.11
Chevron and Clinton v. City of New York raise fundamental questions about the separation of powers. How did we get to a world where executive branch agencies routinely make law and where Congress tries by statute to surrender the most ancient of legislative prerogatives? Was Justice Stevens right to create Chevron deference and then to try to confine that deference in subsequent case law? …