"Like other state--federal challenges, however, this one faces a constitutional hurdle: the supremacy clause, which overrules state law."The supremacy clause referred to in the article is from the US Constitution, art. VI, Paragraph 2. It means in the case of a conflict between state and federal laws, federal law must be followed.
SUPREMACY CLAUSE
"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."
