"Who really runs things around here?" "Who counts?" These questions are old ones, but they are still asked today, as they were in the past. Separation of powers is the doctrine and practice of dividing powers of a government among different branches to guard against abuse of authority (24:563). A government of separated powers assigns different political and legal powers to the legislative, executive, and judicial branches. The legislative branch has the power to make laws-for example, the declaration of what acts are to be regarded as criminal. The executive branch has the authority to administer the law-primarily by bringing lawbreakers to trial-and to appoint officials and oversee the administration of government responsibilities. The judicial branch has the power to try cases brought to court and to interpret the laws under which the trials are conducted. In the United States, the separation of powers is a fundamental constitutional principle. Articles I through III of the Constitution place each of the basic powers of government in separate branches. The legislative power is vested in Congress, the executive power in the president, and the judicial in the Supreme Court and other federal courts.
An important part of the separation of powers is that the power of one branch should not be exercised by anyone who also holds a position in another branch. Under Article I, Section 6, no one elected to Congress may simultaneously serve as a member of the executive branch. In other words, a lawmaker may not also administer the laws. Another important feature of the separation of powers in the United States is the judicial review. The courts, not Congress or the President, say what the law means when a case is before them. In appropriate cases, the courts may even strike down a law enacted by Congress, or order the executive branch to stop enforcement of a law or government policy, if they determine that the law or policy conflicts with the constitution.