Letter: Does federal law trump state law?
Can a state pass and enforce a law that is in opposition to a federal law?
Those who think not cite what is called the Supremacy Clause, which they interpret to say that federal law is supreme over state law. Some would argue that the states cannot pick and choose which laws they wish to honor.
But, what exactly does the Supremacy Clause say? Article Six, Clause Two states: This Constitution, and the Laws of the United States which shall be made in Pursuance thereof … shall be the supreme law of the land.
Those who are unknowing—or are deliberately misleading—contend that this clause says that U.S. law trumps state law.
"Thereof" refers to the Constitution. Laws are to be made in pursuance to the Constitution. What about "shall be made in Pursuance" thereof? Pursuance means following or in keeping with. Thus, only those laws that are in keeping with the Constitution are supreme law of the land. And, those not in keeping with the Constitution are not valid laws. In order for them to be constitutional and enforceable, they must be found in the list of allowable and enumerated laws.
And, who is to say what is constitutional? The states, based on the Constitution itself. If the law is about something that is not listed in the Constitution, then it is unconstitutional and the Supremacy Clause eliminates it as having supremacy over state laws.
The better question would be: When does federal law trump state law? And it is clear that it does so only when the federal law is constitutional, when it is found in the enumerated powers.