Article VI. Section 2. 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.
International treaties that the United States has ratified are a relatively unused source of domestic law. However, the Constitution incorporates by reference these treaties in Article VI, Section 2. Therefore, treaties such as the Universal Declaration of Human Rights are binding in United States courts as much as the U.S. Constitution, federal and state statutes, and judicial precedent.