Arizona SB 1070, signed in April 2010, is the state immigration enforcement law that produced the Supreme Court’s defining ruling on how far states can go in policing immigration. The Court struck down three of its four challenged provisions in 2012 and left only the “status check during a lawful stop” rule standing, and that rule survives under tight limits. In November 2024, Arizona voters added a new layer with Proposition 314, parts of which are already in force and parts of which remain dormant by design.1Justia. Arizona v. United States, 567 US 387 (2012)
What SB 1070 Set Out to Do
The Support Our Law Enforcement and Safe Neighborhoods Act declared a state policy of “attrition through enforcement” and built a parallel state-level enforcement system on top of federal immigration law.2Arizona Legislature. Arizona Senate Bill 1070 It barred local governments from limiting cooperation with federal immigration authorities and expanded police powers in several directions at once.
The four provisions that drew the federal lawsuit were:
- Section 2(B) required officers to make a reasonable attempt to verify immigration status during a lawful contact when they had reasonable suspicion the person was unlawfully present, with status to be confirmed through the federal government.
- Section 3 made it a state crime to fail to carry federal alien registration documents.
- Section 5(C) made it a misdemeanor for an unauthorized immigrant to seek or perform work in Arizona.
- Section 6 authorized state and local officers to arrest someone without a warrant if the officer had probable cause to believe the person had committed an offense making them removable from the country.3Arizona Legislature. Arizona Senate Bill 1070
A separate Section 5 provision (ARS 13-2929) created state penalties for transporting, harboring, or shielding someone the person knew or recklessly disregarded was unlawfully present, with a felony tier for violations involving ten or more people.
One week after the signing, the legislature passed HB 2162, which made two changes before SB 1070 took effect. It added explicit language prohibiting officers from using race, color, or national origin in enforcing the law except as permitted by the U.S. or Arizona Constitution, and it narrowed Section 2(B)’s trigger from any “lawful contact” to a “lawful stop, detention, or arrest.”4Arizona Legislature. SB 1070 as Amended by HB 2162
What the Supreme Court Struck Down
In Arizona v. United States, decided in 2012, the Court applied federal preemption: when Congress has built a comprehensive system in an area, states cannot bolt on their own parallel rules, even rules aimed at the same goals.5Legal Information Institute. Arizona v. United States Three of the four challenged provisions fell.
Section 3 was preempted because Congress has fully occupied the field of alien registration through what the Court called a “single integrated and all-embracing system.” A state cannot add its own registration crime, even one that mirrors federal law.
Section 5(C) was preempted because the Immigration Reform and Control Act of 1986 deliberately imposed criminal penalties on employers but only civil penalties on workers. Arizona’s criminal penalty on workers conflicted with the balance Congress chose.
Section 6 was preempted because allowing state officers to arrest people solely on probable cause of removability inserted the state into the federal removal process without federal direction. Being removable is not itself a federal crime, and the federal government has discretion over when to pursue removal.5Legal Information Institute. Arizona v. United States
What Still Applies Today
Section 2(B), as amended by HB 2162, is the only contested provision that survived. It requires law enforcement to make a reasonable attempt to verify immigration status during a lawful stop, detention, or arrest when the officer has reasonable suspicion the person is unlawfully present.3Arizona Legislature. Arizona Senate Bill 1070
The Court let the provision stand only on a facial challenge, saying it would be “inappropriate to assume” the provision would be applied unconstitutionally before state courts had interpreted it. The majority warned that detaining people solely to verify immigration status “would raise constitutional concerns” and “disrupt the federal framework,” and it left the door open for future challenges based on actual enforcement.1Justia. Arizona v. United States, 567 US 387 (2012)
In practice, an officer can run an immigration status check during a stop they already had legal grounds to make, such as a traffic violation. They cannot extend that stop past the time needed to handle its original purpose just to wait on a status response.
Limits on How Officers Can Use It
The Arizona Attorney General issued an advisory opinion after the ruling that set concrete limits on Section 2(B):
- Officers cannot use race or ethnicity to develop reasonable suspicion that someone is unlawfully present.
- Officers cannot stop someone solely to investigate immigration status.
- Officers cannot hold someone longer than necessary to address the original reason for the stop just to run an immigration check.6Arizona Attorney General’s Office. Advisory Model Policy for Law Enforcement Applying SB 1070
The guidelines also set a presumption of lawful status. You are presumed lawfully present if you show a valid Arizona driver’s license, a valid Arizona non-operating identification license, a valid tribal enrollment card, or any government-issued ID from a jurisdiction that requires proof of legal presence before issuing it. If an officer deviates from the policy, they must notify a supervisor at the first reasonable opportunity.6Arizona Attorney General’s Office. Advisory Model Policy for Law Enforcement Applying SB 1070
What Happened in Maricopa County
The risk the Supreme Court warned about turned real under Maricopa County Sheriff Joe Arpaio. In Melendres v. Arpaio, a federal court found that the sheriff’s office maintained a “custom, policy and practice of racially profiling Latino drivers and passengers” and stopping them under the guise of immigration enforcement.7United States Court of Appeals for the Ninth Circuit. Melendres v. Arpaio
The court permanently barred the sheriff’s office from detaining Latino vehicle occupants based only on a reasonable belief they were unauthorized, from using race or Latino ancestry as a factor in deciding whether to stop a vehicle, and from holding people stopped for traffic violations longer than necessary to resolve the violation without independent suspicion of a separate crime. The court appointed an independent monitor and ordered improvements to training, documentation of traffic stops, and supervisory review. The case remains an active federal oversight matter.
Proposition 314 and What’s Next
Arizona voters approved Proposition 314, the Secure the Border Act, in November 2024. It creates new state-level immigration crimes that reach beyond what SB 1070 attempted. Some provisions are already enforceable.
- A person who is not lawfully present and knowingly submits false documentation when applying for federal, state, or local public benefits commits a class 6 felony.
- Submitting false information to an employer to evade E-Verify detection is a class 1 misdemeanor for a first offense and a class 6 felony for subsequent offenses.
- Knowingly selling fentanyl that was not lawfully manufactured or imported and that caused someone’s death is a class 2 felony.8Arizona Legislature. Proposition 314 Analysis
The most aggressive pieces are not in effect. The provisions making it a state crime to enter Arizona from a foreign country at any location other than a lawful port of entry, and authorizing state officers to order deportations, were deliberately written with a trigger clause tied to the outcome of similar laws in other states. Until a federal court upholds one of those laws, with the Fifth Circuit expected to rehear the challenge to the Texas version in early 2026, Arizona’s entry and removal provisions remain dormant. Two advocacy organizations challenged Proposition 314 in state court in 2025, but a judge dismissed the challenge on the ground that the dormant provisions were not yet ripe for review.8Arizona Legislature. Proposition 314 Analysis
Whether those dormant provisions ever activate depends on how federal courts treat the Texas law, and ultimately on whether the Supreme Court revisits the preemption line it drew in 2012.