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Arizona v. United States
Argued: April 25, 2012
Decided: June 25, 2012
Background
The U.S. Constitution sets up a federalist system of government. This means that the federal
government of the United States and the individual state governments share powers. Some powers
are designated specifically to the federal government, while others are left to the states. Some powers
are shared by both.
When federal and state laws conflict (for example, if a federal law states you must be 18 to vote, and
a state law requires that no one over the age of 18 can vote), the federal law takes precedence. This
power comes from the Supremacy Clause of the Constitution (Article VI, paragraph 2). However,
there isn’t a conflict every time there is a federal and state law about the same subject. For example,
a federal law saying you must be 18 to vote and a state law saying you must register to vote 30 days
prior to an election do not conflict, even though they both concern voting. The issue in this case is
about whether certain federal and state laws conflict with regard to immigration.
The Supreme Court has previously ruled that federal law can preempt state law when:
(a) Congress specifically says so in a federal law,
(b) It is impossible (or very difficult) to comply with both laws, or
(c) The federal law is so comprehensive that there is no room for state laws.
Facts
In 2010, Arizona passed S.B. 1070, a law meant to address problems Arizona felt it was having with
illegal immigration in the state. The law does many things, and four parts are at issue in this case:
1. It makes it a state crime to fail to register as an immigrant or to lack registration papers.
2. It makes it a state crime for undocumented immigrants to work or seek work.
3. It requires local law enforcement officials to check the immigration status of anyone they
stop if there is reasonable suspicion that the person is an undocumented immigrant.
4. It allows local law enforcement officers to arrest anyone that they have probable cause to
believe did something that would get them deported.
The federal government sued Arizona to keep the law from going into effect. The government
believes that S.B. 1070 conflicts with federal immigration law and that Arizona’s law must be
removed. The federal immigration law doesn’t say anything specifically about when it preempts state
laws, so the federal government is relying on the concept that federal law here is so comprehensive
that there is no room for state laws.
The district court ruled for the federal government, and Arizona appealed to the Ninth Circuit Court
of Appeals. That court also ruled for the federal government, and Arizona appealed to the U.S.
Supreme Court.

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Issue
Does federal law preempt Arizona’s immigration law, S.B. 1070?
Constitutional Clauses and Precedents
The Supremacy Clause- U.S. Constitution, Article VI, Paragraph 2
“This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; …
shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any
Thing in the Constitution or Laws of any State to the Contrary notwithstanding.”
Hines v. Davidowitz (1941)
Pennsylvania passed an Alien Registration Act that contradicted the U.S.’s system of registering
foreigners. For example, the Pennsylvania law required foreigners to register every year, while the
federal law only required foreigners to register once. The Supreme Court ruled that Pennsylvania’s
law was preempted, saying “states cannot, inconsistently with the purpose of Congress, conflict or
interfere with, curtail or complement, the federal law, or enforce additional or auxiliary regulations.”
Buckman Co. v. Plaintiffs Legal Committee (2001)
A state law that intended to prevent fraud against the Food and Drug Administration required
applicants for FDA approval to submit extra information to the FDA. The Supreme Court ruled
that this law was preempted by federal law, because it created a burden on the FDA. The FDA said
they didn’t need the extra information, and didn’t want applicants to submit it. Although the state
law was designed to further the goals of the FDA, it actually had the effect of making their work
more difficult.
Chamber of Commerce v. Whiting (2011)
The Supreme Court upheld an Arizona law that penalized employers who knowingly hired
undocumented immigrants as workers, and required employers to use a federal immigrant status
verification system. The law took away a business’s right to operate in Arizona if they violated it, and
the federal government argued that was preempted by a federal law about employment. The
Supreme Court concluded that the state law did not conflict with the federal law because the federal
law specifically allowed states to impose penalties for hiring unauthorized workers through business
licensing and similar laws.

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Arguments for the United States
 Congress has passed laws that completely regulate immigration, leaving no room for state
laws about when to detain or penalize immigrants or check immigration status. The federal
government has given the executive branch authority to decide how to enforce these laws.
Arizona’s law intrudes on the federal government’s control over immigration.
 The Constitution empowers Congress to “To establish a uniform Rule of Naturalization”
and “To make all Laws which shall be necessary and proper for carrying into Execution the
foregoing Powers.” Immigration policy is something that needs to be done at the federal
level, because uniformity is needed across the country. Arizona’s law disrupts that necessary
uniformity.
 Immigration enforcement affects foreign relations, which is the exclusive domain of the
federal government. Arizona’s law could have implications for the United States’ relationship
with foreign countries.
 The executive branch has put priorities on enforcing certain aspects of immigration law over
others – something that federal law entitles them to do. For example, the federal
government has decided to devote its limited resources to deporting immigrants who
commit crimes over immigrants who have not. In some cases, the federal government
doesn’t want to deport undocumented people because they are witnesses in criminal cases,
or because they’ve applied for asylum. Arizona’s law undermines these federal priorities.
 There are some issues that federal immigration law does not address, such as penalties for
immigrants who solicit work. Those are not oversights or gaps, however Congress
purposefully chose not to penalize people for seeking work, so Arizona can’t either.
 The states are allowed to cooperate with the federal government to help enforce federal law.
Arizona isn’t cooperating, though – it’s competing.
 If the Arizona law is allowed, then every state could pass different immigration laws. We
can’t have a patchwork of uneven immigration laws and enforcement priorities existing in
different states.

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Arguments for Arizona
 While Congress has the power to “To establish a uniform Rule of Naturalization,” the
federal government’s regulations are not so comprehensive that they eliminate the need for
state laws. In Chamber of Commerce v. Whiting, the Supreme Court ruled that Arizona’s law
requiring employers to verify immigration status could exist alongside federal law.
 S.B. 1070 cooperates with and complements federal law. The law simply adopts as state
crimes some things that are already federal crimes. There may be a conflict between the
federal government’s enforcement policy and the Arizona law, but that doesn’t matter. What
matters is whether there is a conflict between the federal law and the state law. Arizona law
just prohibits the same conduct that federal law prohibits.
 State officials can enforce federal laws – in fact, the federal government needs the help of
state officials. State law enforcement officers arrest people for committing federal crimes, for
example. States have inherent police powers, reserved to them by the Constitution. Arizona
simply put into writing what cops across the country are already doing.
 Arizona’s law is consistent with the purpose of the federal law regarding employment. The
purpose of the federal law is to discourage employment of undocumented immigrants. The
federal government has penalized the supply side (employers), and Arizona is penalizing the
demand side (job seekers) in order to fill the gaps the federal law left open and to help
achieve the law’s purpose.
 S.B. 1070 isn’t like the laws at issue in either Hines v. Davidowitz or Buckman Co. v. Plaintiffs
Legal Committee. It doesn’t conflict or interfere with federal law, and it doesn’t burden a
federal agency.
 The federal government isn’t effectively dealing with the challenges of illegal immigration.
Arizona, as a border state, absorbs a great number of immigrants, and should be able to
create laws to address in-state problems when the federal government is unable or unwilling
to do so.

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Decision
The Supreme Court ruled that three of the four provisions of Arizona’s law were preempted by
federal law. Justice Kennedy wrote the majority opinion. He was joined by Chief Justice Roberts and
Justices Ginsburg, Breyer, and Sotomayor. Justices Scalia and Thomas each filed opinions agreeing
with the majority about one provision of the law that was not struck down but otherwise dissenting.
Justice Alito filed an opinion agreeing with the majority on two provisions. Justice Kagan did not
take part in the decision because she had been involved with the case as Solicitor General.
Majority
The Supreme Court agreed with the United States that the federal government has a broad power
over immigration due to its constitutional power to “establish a uniform Rule of Naturalization,”
and that the Federal Government has used this power to create a comprehensive set of laws
governing immigration. Since the Supremacy Clause gives Congress the power to trump state laws,
any laws that conflict with the comprehensive federal immigration law should be struck down. Using
this reasoning, the Court said that three parts of the law are preempted by federal law:
 The provision making it a state crime to fail to register as an immigrant or lack immigration
papers. Even though this provision meant to complement existing federal laws, the federal
laws dealing with immigrant registration are so comprehensive that they do not allow for
additional state regulation.
 The provision making it a crime for undocumented immigrants to work. The Court said that
it was clear from the history of the federal immigration laws that Congress purposefully
chose not to punish undocumented workers in this way and so the provision was preempted.
 The provision allowing law enforcement officials to arrest anyone that they had probable
cause to believe did something that would get them deported. This provision would bypass
the typical requirement for a warrant before an arrest and as such goes beyond merely
cooperating with the federal law.
The fourth provision, requiring officers to check the immigration status of anyone they stop or
detain if there is reasonable suspicion that the person is an undocumented immigrant, was left in
place. So long as the implementation of this part of the law does not cause people to be detained
longer than they would be otherwise and does not result in a violation of civil rights through some
sort of racial profiling, the Court said, it is constitutional.
Dissent
Justices Scalia and Thomas argued that there was no conflict between any part of Arizona’s law and
federal immigration law. Arizona is sovereign, they said, and even though its laws must be second to
those of the United States if they actually conflict, an important part of sovereignty is the right to
defend borders. The dissenters argued that if the federal government is not enforcing its own laws,
then at the very least the state governments ought to have the right to enforce them. Justice Alito
would have upheld two of the provisions and struck the other two down.