The framers of the constitution knew that accumulation of all powers in the same hands would result in tyranny. In their effort to prevent tyranny and to form a more perfect union, they undertook to separate the legislative, the executive and the judicial powers in the first three articles of the Constitution. But, knowing equally well that an absolute separation would only impair the effective function of the government, they also rejected a total separation of powers.
The result was a government of separated institutions sharing powers“, whose structure incorporated the concept of checks and balances. Within this structure, the departments are formally separated and each was assigned certain core functions, but their functions are also mingled and blended. The separate governmental departments are independent from one another, yet they exercise a mutual control function in order to prevent a misuse of power.
As Justice Brandeis said, disenting in Myers v. United States(1962):
The doctrine of the separation of powers was adopted by the Convention of 1787, not to promote efficiency, but to preclude the exercise of arbitrary power. The purpose was not to avoid friction, but, buy reasons of the inevitable friction incident to the distribution of the governmental powers among three departments, to save the people from autocracy.
Thus, under this scheme of government, the legislative and the executive branches are independent from and exercise a mutual check upon each other. The president is independently elected. Members of Congress are not permitted to seek office in the executive and judicial branches of government. The president appoints officials, but only with the consent of the Senate. The president makes treaties, but the Senate must give its advice and consent to make them effective. As commander-in-chief of the armed forces, the president may dispatch troops abroad, but only Congress can declare war and authorize the necessary finances. The president is not subject to the legislative control for his political acts, but he may be impeached by congress for treason, bribery, or other high crimes and misdemeanors. Congress can legislate, but the president can veto. After the presidential veto, Congress can override it by a two-thirds majority of votes in both houses. The president appoints judges, with the approval of the Senate, but the laws made by Congress and signed by the president are subject to judicial review.
The doctrine of judicial review plays an important role in the whole scheme of checks and balances. Judicial review does not rest on any express provision of the Constitution but derives from its basic philosophic values and from constitutional traditions. It was established by the Supreme Court decision in Marbury v. Madison(1803). In that case the Supreme Court decided that judicial control was not limited to the review of state law for its constitutionality. It extended to examination and review of federal laws as well. This basic decision gives effect to the principle of separation of powers, making it an actionable claim for the enforcement and observance of the rule of law.
Judicial control over the president (in contrast to inferior branches of the executive departments) logically derives from the same Constitutional tradition. But it was not until 1952 that the courts had an opportunity to exercise that control. In Youngstown Sheet & Tube v. Sawyer, the Supreme Court declared emergency measures of President Truman to be an unconstitutional exercise of legislative power. The issue of judicial control over the president arose anew in 1973 and 1974 in the famous controversy over Nixon's involvement in the Watergate scandal. When Nixon refused to obey, on ground of executive privileg, an order of a federal judge to produce certain tapes, the Supreme Court affirmed the order of the district court. In doing so, it reaffirmed that it was the duty of the Supreme Court to say what the law is with respect to the claimed privilege. The significance of this decision, United States v. Nixon, is similar to Marbury v. Madison. It concludes the system of judicial control and assures the observance of the rule of law and separation of powers in the governmental structure.