Legislatures create laws, executive officials enforce laws, and judges adjudicate disputes. The Constitution of the United States creates a three-branch system, with Congress to create law, the president to enforce laws, and federal courts to adjudicate disputes. State constitutions establish similar structures for their governments. This is an incomplete picture of government.

Federal, state, and local administrative agencies have become important vehicles for the implementation of policies, services, the creation of law, the enforcement of law, and the adjudication of disputes. Indeed, agencies make more laws than Congress, enforce more laws than the president, and adjudicate more “cases” than the courts. Yet, they are not mentioned in the U.S. Constitution.

Because the number of agencies in the United States has grown significantly in recent years, as has the authority of these agencies, a body of law has developed to control and regulate their behavior and function. This is known as administrative law. Administrative law defines the powers, limitations, and procedures of administrative agencies.