Answer: Supremacy Clause of the Constitution
Step-by-step explanation:
Federal law is superior to State Law and this is enshrined in the Constitution by the Supremacy Clause which essentially states that the Constitution and Federal laws are the highest law of the land and state laws or constitutions cannot violate them.
If there is a conflict between the Constitution and state law, the Constitution takes precedence and if there is uncertainty as to whether there is a conflict, Federal courts can be approached all the way to the Supreme Court.