Federal Law and The Hierarchy of Authority
The United States Constitution is the supreme law of the land. All federal law must conform with the Constitution.
There are four types of federal law. These four types are called "primary law." In hierarchical order of authority (highest to lowest authority) they are:
The hierarchy of authority is important because it enables plaintiffs to challenge United States Codes (legislation passed by Congress) and Administrative Law (law written by unelected bureaucrats) as unconstitutional.
Federal Law vs State Law
Article VI of the Constitution contains the Supremacy Clause, which dictates that federal law is higher than state law. State judges must follow the U.S. Constitution, laws, and treaties of the federal government in matters which are directly or indirectly within the government's control.
Under the doctrine of preemption, which is based on the Supremacy Clause, federal law preempts state law, even when the laws conflict. Thus, a federal court may require a state to stop certain behavior it believes interferes with, or is in conflict with, federal law.