What is preemption?

Federal preemption is a legal term used when the Constitution or Congress give the federal government exclusive power to legislate on an issue. Under the Constitution, federal law is the supreme law of the land, and when a state law clashes with federal law, it's up to the courts to decide whether the state law is preempted by federal law. If a judge decides that either a specific provision or the entire state law is preempted, the measure is declared unconstitutional.

What does the Constitution say about preemption?

The preemption doctrine derives from the Supremacy Clause in the Constitution (Article VI, clause 2), which says that when there's a conflict, the Constitution and federal law are the supreme law of the land. This doctrine works like a kind of tie breaker, giving the upper hand to Congress when it gets into turf battles with the states. When Congress is empowered by the Constitution to legislate on an issue, it preempts or overrides related state legislation.

Who can make immigration law – Washington or the states?

Which branch of government has the power to make immigration law is a complex legal issue currently being disputed in courts across the country.

For more than a hundred years, immigration law was considered a federal prerogative – a realm in which the states had virtually no role to play. That changed dramatically in recent years as congressional inaction led many state and local jurisdictions to take matters into their own hands, passing measures to crack down on illegal immigration. Many of these state laws have been challenged in court, and the decisions have been inconsistent. The U.S. Supreme Court ruled on one facet of the issue in May 2011 and will rule on another in coming months – but even then many questions will remain undecided. Bottom line: immigration is a very uncertain area of the law, and states venture in at their own risk.

What did the Supreme Court decide about state laws mandating E-Verify?

The Supreme Court’s May 2011 decision in the U.S. Chamber of Commerce v. Whiting case ruled that Arizona was within its rights to mandate E-Verify and use state licensing provisions to sanction employers found to have hired unauthorized workers.

The 5-3 decision was based on the court's expansive interpretation of the IRCA savings clause. Chief Justice John Roberts, writing for the majority, said the Legal Arizona Workers Act "falls well within the confines of the authority Congress chose to leave to the states." According to the majority, the Arizona law does not conflict with federal immigration enforcement, and the federal statute establishing E-Verify does not constrain state action. In other words, in this specific case – worksite immigration enforcement involving state business licenses – there is no need to choose between federal and state law, so both are valid.

Where does this leave states considering mandating E-Verify?

The Supreme Court's Whiting decision created some room to maneuver for states considering immigration enforcement. But the ruling was decided on very narrow grounds – the court's interpretation of a seven-word parenthesis. And it dealt with only one kind of state immigration enforcement: employer sanctions laws involving state business licenses.

In the wake of the decision, states may require employers to enroll in E-Verify, and states may suspend or revoke the business licenses of employers found to have hired unauthorized immigrants. That, the court said, is constitutional. But Whiting did not open the door to any other kind of state immigration enforcement – policing laws, restrictions on
government benefits, laws mandating the collection of data about immigration status or any others.


ImmigrationWorks USA,
Preemption: Who should make immigration law? January 2011

Migration Policy Institute, Supreme Court LAWA decision: Implications for other state immigration laws, June 2011

UC Davis School of Law, Federal preemption, July 2011

Law Office of James Deans, What is preemption and how does it affect state laws? November 2011

International Business Times, SCOTUS case on Arizona's policing law poses federal preemption issue, January 2012