The Supremacy Clause asserts that the United States Constitution is the supreme Law of the Land, and that judges and any other seat of authority in a state are bound to follow the Constitution, the laws of the United States and any treaties made under the authority of the United States, as passed by the United States Congress, and as carried out by the President of the United States of America. Any rule of any state is null if contrary to these laws.
The text of the clause is as follows:
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.
The Supremacy Clause is a part of United States Constitution:Article VI, section 2.
For a more detailed treatment, see Federal preemption.
The preemption doctrine is a principle derived from the supremacy of the Constitution. It applies mainly due to the need for preventing conflicts between federal and state law.
When a conflict is not clear as to which law should apply, the Supreme Court will generally try to follow the intent of lawmakers. In Ware v. Hylton, a statue was passed in the state of Virginia which secured debt payments to creditors in Britain. The Treaty of Paris contains clauses for the treatment of British creditors, so to be consistent with the Supremacy Clause and the Constitution's delegated power of treaty making, the Virginia law was held to be "null and void".