THE GENERAL PRINCIPLES OF CONGRESSIONAL OVERSIGHT
What is the Basis for Congressional Oversight?
Congressional oversight is one of the most important responsibilities of the United States Congress. Congressional oversight refers to the review, monitoring, and supervision of federal agencies, programs and policy implementation, and it provides the legislative branch with an opportunity to inspect, examine, review and check the executive branch and its agencies. The authority of Congress to do oversight is derived from its implied powers in the U.S. Constitution, various laws, and House rules. In affirming Congress' oversight powers, the Supreme Court in McGrain v. Daugherty stated that "the power of inquiry – with process to enforce it – is an essential and appropriate auxiliary to the legislative function." In Watkins v. United States the Court described Congress' oversight power by stating that the "power of the Congress to conduct investigations is inherent in the legislative process. That power is broad." The Supreme Court also observed that "a legislative body cannot legislate wisely or effectively in the absence of information respecting the conditions which the legislation is intended to affect or change." The Legislative Reorganization Act of 1946 mandated that House and Senate committees exercise "continuous watchfulness" of the administration of laws and programs under their jurisdiction. The Legislative Reorganization Act of 1970 permitted House standing committees to "review and study, on a continuing basis, the application, administration and execution of laws" under its jurisdiction.
http://www.rules.house.gov/archives/comm_gp_cong_oversight.htm