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.
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; and the Judges in every State shall be bound thereby, any thing in the Constitution or Laws of any State to the Contrary notwithstanding.