The "Supreme Law of the Land" in the United States is the Constitution. This provision is stipulated in Paragraph 2 of Article 6 of the U.S. Constitution, also referred to as the "Supremacy Clause." The clause mandates that federal statutes and international agreements legally precede state laws.
The U.S. Constitution is a "living document" containing the provisions for the basic rights of the American people, the creation of government and its structure and the necessary limitations to prevent the potential abuse of vested powers. The judiciary branch is tasked to interpret and uphold the Constitution. Congressional bills that are deemed as unconstitutional are not enacted into laws.