Article VI establishes that the “Constitution, and the Laws of the United States . . . made in Pursuance thereof; and all Treaties 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. . . .” Thus, state court judges must follow the U.S. Constitution, even when state laws conflict with it. The Supreme Court’s power to assess the constitutionality of state legislation logically extends from its role as the ultimate arbiter of the Constitution.
The Supreme Court contends that review of state law is essential to the development of uniform constitutional principles. The Constitution would have little effect if each state were free to apply the document as it saw fit.