The United States has a federal system. Federalism is a form of government in which power is divided. Power is shared between a federal, or national, government and state governments. Our federal government is based in Washington, D.C. Congress is the body that makes federal laws.
The U.S. form of federalism is based on the U.S. Constitution. The Constitution declares that federal laws are the "supreme law of the land." Only the Constitution is above federal law. No law can go against the Constitution.
The Federal Government Shares Power with the States
The federal government has many great powers. It can charge taxes. It can create federal courts. It can declare war.
However, the Constitution limits the federal government's powers. The federal government's power is shared with the states.
States are given the powers needed to protect public safety and health. Such powers are called "police powers."
Certain powers are called "concurrent powers." These are powers that states and the federal government both have. They both use these powers at the same time. One such power is the power to charge taxes. Another is the power to spend and borrow money.
There Can Be Conflicts
It is not always clear if the power to make certain laws belongs to the federal or state government. As a result, two very different laws covering the same thing can be passed. This can lead to conflict. The two laws can work against each other.
The Constitution provides a way to settle such conflicts. This is known as the doctrine of preemption. A doctrine is a rule. To preempt is to overrule. Under the doctrine, if a state law conflicts with a federal law, the state law must give way. States are not allowed to block federal laws.
State Laws Cannot Go against Federal Laws
Federal law can preempt state law for various reasons. Sometimes federal and state laws clearly contradict each other. One law says one thing. The other says the opposite.
State laws are also preempted when it is impossible for someone to follow both state and federal laws. Finally, state laws are preempted when they undercut a federal law. These laws go against the goal of a federal law.
The doctrine of preemption does not always apply, however. It does not apply when a federal law goes against the Constitution. In that case, the state law would win out. The Constitution is the final judge.