<P> In Cooper v. Aaron, 358 U.S. 1 (1958), the Supreme Court rejected attempts by Arkansas to nullify the Court's school desegregation decision, Brown v. Board of Education . The state of Arkansas, acting on a theory of states' rights, had adopted several statutes designed to nullify the desegregation ruling . The Supreme Court relied on the Supremacy Clause to hold that the federal law controlled and could not be nullified by state statutes or officials . </P> <P> In Edgar v. MITE Corp., 457 U.S. 624 (1982), the Supreme Court ruled: "A state statute is void to the extent that it actually conflicts with a valid Federal statute". In effect, this means that a State law will be found to violate the Supremacy Clause when either of the following two conditions (or both) exist: </P> <Ol> <Li> Compliance with both the Federal and State laws is impossible </Li> <Li> "State law stands as an obstacle to the accomplishment and execution of the full purposes and objectives of Congress" </Li> </Ol> <Li> Compliance with both the Federal and State laws is impossible </Li>

According to the u.s. constitution's national supremacy clause