The supremacy clause of Article VI, clause 2, declares: "This Constitution and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the authority of the United States, shall be the supreme law of the Land." This principle of national supremacy was a radical departure from the constitutional order that prevailed under the ARTICLES OF CONFEDERATION. Whereas the Articles created a short-lived confederation of states?according to its terms a mere "league of friendship" founded on the good faith of sovereign states?the Constitution established a federal union designed to last in perpetuity. The distinguishing feature of the "more perfect union" created by the Constitution was a strong national government capable of dealing with the problems and complexities of a growing nation and strong state governments acting within their sphere of authority. The Constitution does not establish the supremacy of the national government in all things. National supremacy is limited to laws made Pursuant to the Constitution. What is not granted to the national government under its ENUMERATED POWERS is, as a general rule, reserved to the people or to the states under the TENTH AMENDMENT.
The supremacy clause may truly be regarded as the linchpin of American FEDERALISM. It holds the republic together by providing a principle for the resolution of conflicts between the states and the nation. Valid national law is clearly paramount in the face of conflicting state law. But whether a state law conflicts with federal law or a federal constitutional provision is not always clear. When doubts exist over the compatibility of federal and state law, and a real controversy arises from these doubts, the judiciary is usually called upon to work out the implications of the supremacy clause through interpretation. The outcome of such cases often depends on inferences drawn by the courts from the structure of the federal system and the values it represents.
The problems of interpretation generated by the supremacy clause have taken two forms epitomized by the celebrated cases of MCCULLOCH V. MARYLAND (1819) and GIBBONS V. OGDEN (1824). In the first Maryland taxed a national bank doing business within its borders; in the second
New York granted a monopoly over steamboat navigation on its internal waterways. The supremacy clause operated to invalidate both measures. McCulloch stands for the principle that even a power reserved to the states?here the ordinary and indispensable power of taxation?may not be exercised in such a way as to impede or unduly burden a federal agency or activity; Gibbons stands for the principle that the state's regulation of a subject matter within its territory, and normally under...