In a legal context, preemption refers to the principle that certain matters which have a national effect are governed by federal laws, rather than any contradictory state or local laws that may exist. This doctrine is based on the U.S. Constitution’s Supremacy Clause, which specifies that federal law preempts inconsistent state law. To explore this concept, consider the following preemption definition.

Definition of Preemption


  1. A legal doctrine in which federal law supersedes, or “preempts,” state law when the two are in conflict one with another.


1595-1605       Latin     praeëmpt -us    (brought beforehand)

What is the Doctrine of Preemption

The Tenth Amendment of the U.S. Constitution dictates that any powers that are not specifically delegated to the federal government are under the authority of the individual states. Over the years, the concept of federal supremacy evolved, taking into account that some states may pass laws which conflict with the Constitution, or with federal law.

Early in the 20th century, the Supreme Court embraced the Supremacy Clause, found in Article VI, Section 2 of the U.S. Constitution, which specifies that the “Constitution, and the laws of the United States … shall be the supreme law of the land.” The Court held that the federal government cannot be subjected to the laws of any state.

Federal Preemption

Over the years, there have been many circumstances in which federal laws and regulations have preempted state and local laws. In some situations, Congress has passed or upheld federal legislation that preempts all state laws, in others, Congress allows a federal regulatory agency to set federal minimum standards. In such a situation, there is no federal presumption over state criteria or guidelines that are more stringent than federal standards.

For example:

John owns and operates more than 200 vending machines in various schools and offices in a large city. His most popular products are super-caffeinated energy boosting drinks, which are a favorite of high school and college students. John discovers the state in which he operates his business has passed a law that prohibits the sale or distribution of highly caffeinated drinks anywhere in the state.

When John fails to remove these products from his vending machines, he is charged with violating state law. John knows, however, that there is a federal law prohibits bans on caffeinated drinks. John can challenge the charges based on the fact that the state’s law is preempted by federal law.

In some circumstances, whether or not state laws conflict with existing federal laws is unclear. These are the questions brought before the U.S. Supreme Court. As a rule, the Court has shown a preference for not preempting state laws. As such, the Court generally attempts to understand the intent of lawmakers, both federal and state, to come up with a ruling that is in the best interests of the people.

Federal Exemption in Colorado’s Marijuana Law

After the state of Colorado legalized the commercial growing and distribution of marijuana, neighboring states saw a steep rise in marijuana-related crimes. In December 2014, the states of Nebraska and Oklahoma asked the U.S. Supreme Court to allow them to file a lawsuit against the state of Colorado, claiming that Colorado has failed to keep its marijuana within its borders. There is a little-used rule that allows one state to sue another state in the U.S. Supreme Court, without first suing in a lower court. This may only be done if the Supreme Court first gives permission.

The basis of the Nebraska/Oklahoma lawsuit is that, according to Article VI of the U.S. Constitution, no state may authorize the violation of federal law. Nebraska and Oklahoma claim Colorado’s unconstitutional law has caused them financial and legal hardship, as their costs for enforcement, including making arrests, impounding vehicles, seizing drugs, and housing criminals, have greatly increased.

Nebraska and Oklahoma are asking the Supreme Court to rule, based on the principle of federal preemption, that Colorado must stop allowing marijuana to be grown and distributed on a commercial basis, as this violation of federal law damages the states’ marijuana prevention and enforcement programs.

Some legal professionals, as a result of this action, have expressed the belief that, because federal law preempts Colorado’s marijuana laws, it would be more appropriate for the states to force the U.S. Attorney General to enforce federal law. While, as of August 2015, the Supreme Court had not made its decision on whether to allow Nebraska/Oklahoma to file an original jurisdiction lawsuit, the Court’s next moves could have a serious impact on how other states deal with marijuana legislation.

Related Legal Terms and Issues

  • Civil Lawsuit – A lawsuit brought about in court when one person claims to have suffered a loss due to the actions of another person.
  • Original Jurisdiction Lawsuit – A court’s authority to hear and decide a case, before an appeal. The trial court must have original jurisdiction over the types of cases it hears.