The Supremacy Clause of the Constitution of the United States (Article VI, Clause 2) establishes that the Constitution, federal laws made pursuant to it, and treaties made under its authority, constitute the "supreme Law of the Land", and thus take priority over any conflicting state laws. It provides that state courts are bound by, and state constitutions subordinate to, the supreme law. However, federal statutes and treaties must be within the parameters of the Constitution; that is, they must be pursuant to the federal government's enumerated powers, and not violate other constitutional limits on federal power, such as the Bill of Rights—of particular interest is the Tenth Amendment to the United States Constitution, which states that the federal government has only those powers that are delegated to it by the Constitution.
The Supremacy Clause is essentially a conflict-of-laws rule specifying that certain federal acts take priority over any state acts that conflict with federal law. Some jurists further argue that the clause also nullifies federal law that is in conflict with the Constitution, although this is disputed. The Supremacy Clause follows Article XIII of the Articles of Confederation, the predecessor of the Constitution, which provided that "Every State shall abide by the determination of the [Congress], on all questions which by this confederation are submitted to them."
As a constitutional provision announcing the supremacy of federal law, the Supremacy Clause assumes the underlying priority of federal authority, albeit only when that authority is expressed in the Constitution itself; no matter what the federal or state governments might wish to do, they must stay within the boundaries of the Constitution. Consequently, the Supremacy Clause is considered a cornerstone of the United States' federal political structure.
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Background
Constitutional Convention
According to Madison's Notes of Debates in the Federal Convention of 1787, the Supremacy Clause was introduced as part of the New Jersey Plan. During the debate, it was first put up for a motion by Luther Martin on July 17, when it passed unanimously.
During Pennsylvania's ratifying convention in late 1787, James Wilson stated, "the power of the Constitution predominates. Anything, therefore, that shall be enacted by Congress contrary thereto, will not have the force of law."
The Federalist Papers
In Federalist No. 33, Alexander Hamilton writes about the Supremacy Clause that federal laws by definition must be supreme. If the laws do not function from that position, then they amount to nothing, noting that "A law, by the very meaning of the term, includes supremacy. It is a rule which those to whom it is prescribed are bound to observe. This results from every political association. If individuals enter into a state of society, the laws of that society must be the supreme regulator of their conduct. If a number of political societies enter into a larger political society, the laws which the latter may enact, pursuant to the powers entrusted to it by its constitution, must necessarily be supreme over those societies, and the individuals of whom they are composed."
In Federalist No. 44, James Madison defends the Supremacy Clause as vital to the functioning of the nation. He noted that state legislatures were invested with all powers not specifically defined in the Constitution, but also said that having the federal government subservient to various state constitutions would be an inversion of the principles of government, concluding that if supremacy were not established "it would have seen the authority of the whole society everywhere subordinate to the authority of the parts; it would have seen a monster, in which the head was under the direction of the members".
Alexander Hamilton, wrote in Federalist No. 78 that, "There is no position which depends on clearer principles, than that every act of a delegated authority, contrary to the tenor of the commission under which it is exercised, is void. No legislative act, therefore, contrary to the Constitution, can be valid."
Preemption doctrine
The constitutional principle derived from the Supremacy Clause is federal preemption. Preemption applies regardless of whether the conflicting laws come from legislatures, courts, administrative agencies, or constitutions. For example, the Voting Rights Act of 1965, an act of Congress, preempts state constitutions, and Food and Drug Administration regulations may preempt state court judgments in cases involving prescription drugs.