Local police can enforce immigration law only in limited ways. Under the Supreme Court’s 2012 decision in Arizona v. United States, an officer who has lawfully stopped you for some other reason may check your immigration status and share what they learn with federal authorities, but they cannot stop, detain, or arrest you just because they suspect you are undocumented. That baseline changes in jurisdictions that have signed a 287(g) agreement with Immigration and Customs Enforcement, a formal partnership that deputizes trained local officers to carry out specific federal immigration functions. As of September 2025, ICE reported more than 1,000 of these agreements across 40 states.1U.S. Department of Homeland Security. DHS 287(g) Reaches More Than 1,000 Partnerships with State and Local Enforcement So the real answer depends on where you are.
Why Immigration Is Primarily a Federal Job
The Constitution gives Congress the power over naturalization, and the Supreme Court has long treated immigration as an exclusively federal domain. States and cities cannot write their own immigration codes or decide on their own how the Immigration and Nationality Act should be enforced. When a state law covers the same ground as federal immigration law, the federal version wins.
In Arizona v. United States, the Court struck down several provisions of Arizona’s SB 1070 on this basis. Making it a state crime to fail to carry federal registration documents was preempted because Congress had already occupied the field of alien registration. A state law criminalizing unauthorized work was struck down because federal law had deliberately chosen to penalize employers rather than workers.2Cornell Law Institute. Arizona v. United States States cannot layer their own criminal penalties on top of the federal framework even when they are trying to address the same problem.
What Local Officers Can Do During a Lawful Stop
The one SB 1070 provision the Court left standing was Section 2(B), which requires officers to check immigration status during a lawful stop, detention, or arrest when there is reasonable suspicion the person lacks authorization. The Court reasoned that this did not necessarily conflict with federal law because Congress had already encouraged information-sharing between local and federal agencies.2Cornell Law Institute. Arizona v. United States
In practice, an officer who pulls you over for a traffic violation and develops a reasonable basis to suspect you lack immigration authorization can run your name through a federal database. If the check turns up an outstanding removal order or other flag, the officer can pass that information to ICE. This is a communication function, not an independent enforcement power. The officer is making a phone call, not an immigration arrest.
What Local Officers Cannot Do
The firm line: local police cannot stop, detain, or arrest you solely because they believe you may be undocumented. There has to be an independent legal basis for the encounter first, such as a traffic violation or suspected criminal activity. Pulling someone over because they “look like” they might not have papers is an unlawful seizure under the Fourth Amendment.
A lot of confusion comes from a misunderstanding about what kind of violation unauthorized presence actually is. Entering the country illegally is a federal crime, a misdemeanor on a first offense carrying up to six months in prison and a felony with up to two years for a subsequent offense.3Office of the Law Revision Counsel. 8 U.S. Code 1325 – Improper Entry by Alien But simply being present in the country without authorization, which describes millions of people who overstayed a visa, is a civil violation of the INA. Local officers generally cannot make warrantless arrests for federal misdemeanors they did not personally witness, and they have no authority at all to arrest for civil immigration violations.
ICE Detainers Are Requests, Not Warrants
When ICE identifies someone in a local jail who may be removable, it often issues a detainer, a written request asking the jail to hold the person for up to 48 hours past their scheduled release so ICE can take custody.4U.S. Immigration and Customs Enforcement. Immigration Detainers A detainer is not a judicial warrant. Multiple federal courts have held that jailing someone past their release date based only on a detainer, with no warrant signed by a judge, violates the Fourth Amendment. Localities that honor detainers without judicial authorization can face liability for the extra detention, and some have paid substantial settlements.
The 287(g) Program Changes the Picture Locally
Section 287(g) of the INA lets ICE sign a written agreement with a state or local law enforcement agency, delegating specific immigration enforcement powers to trained local officers.5Office of the Law Revision Counsel. 8 USC 1357 – Powers of Immigration Officers and Employees Officers who complete ICE training can then question people about immigration status, issue detainers, and initiate removal proceedings, all under federal supervision.
The scale has grown sharply. ICE reported more than 1,000 active 287(g) agreements across 40 states as of September 2025, a 641 percent increase from the 135 agreements that existed under prior administrations.1U.S. Department of Homeland Security. DHS 287(g) Reaches More Than 1,000 Partnerships with State and Local Enforcement The most common arrangement is the jail enforcement model, where deputized officers screen people booked into a local jail. A less common task force model gives trained officers limited immigration authority during field operations.
Only officers who have completed ICE training can exercise these powers, and they operate under federal direction. The statute places the cost on the state or locality, though the current administration has offered to reimburse participating agencies for salaries, overtime, and start-up costs.5Office of the Law Revision Counsel. 8 USC 1357 – Powers of Immigration Officers and Employees If you want to know whether local officers in your area carry this expanded authority, ICE publishes the list of participating agencies by state.
Sanctuary Policies and the Current Federal Fight
Hundreds of cities and counties have adopted policies that limit their cooperation with federal immigration enforcement. These “sanctuary” policies, a political label rather than a legal one, typically direct jails to decline ICE detainers that lack a judicial warrant and prohibit officers from asking about immigration status during routine encounters. The stated goals are to conserve local resources for local crime and to encourage immigrant residents to report crimes without fear of deportation.
The legal foundation is the anti-commandeering doctrine under the Tenth Amendment. In Printz v. United States and New York v. United States, the Supreme Court held that the federal government cannot force state and local officials to administer or enforce a federal program. Declining to do ICE’s job for free fits within that principle.
The friction point is 8 U.S.C. § 1373, which says no government entity may prohibit or restrict the sharing of immigration status information with federal immigration authorities.6Office of the Law Revision Counsel. 8 U.S. Code 1373 – Communication Between Government Agencies and the Immigration and Naturalization Service The federal government has used this statute to argue sanctuary policies are illegal and to threaten federal grant money. Courts have pushed back. In 2025, a federal court issued a preliminary injunction blocking the administration from withholding or freezing federal funding from jurisdictions labeled as sanctuary cities, finding the tactic likely violated the Tenth Amendment and separation of powers. The law here is actively contested and shifting.
A Note on the Border Zone
If you live within 100 miles of a U.S. border or coastline, you may encounter immigration enforcement that looks like local policing but is not. Customs and Border Protection agents can operate checkpoints, board vehicles, and question people about citizenship within a “reasonable distance” from any external boundary, defined by regulation as 100 air miles.7U.S. Customs and Border Protection. Legal Authority for the Border Patrol Roughly two-thirds of the U.S. population lives within that zone. These are federal agents acting under federal authority. Your city or county police do not gain any expanded powers because you live near a border.
Your Rights During a Police Encounter
These protections apply whether you are a citizen or not.
- You have the right to remain silent. You do not have to answer questions about where you were born, whether you are a citizen, or how you entered the country.
- If you are driving, you must provide your license, registration, and proof of insurance. You do not have to answer questions unrelated to the stop.
- You can refuse consent to a search of your person, vehicle, or belongings by stating clearly, “I do not consent to a search.”
- If you are arrested, say that you want to speak with a lawyer before answering questions.
- If you are not a U.S. citizen and are arrested, you have the right to contact your country’s consulate.8eCFR. 28 CFR 50.5
Federal law requires noncitizens 18 and older to carry their registration documents, such as a green card, employment authorization card, or visa, and failure to do so is a federal misdemeanor punishable by a fine of up to $100 or up to 30 days in jail.9Office of the Law Revision Counsel. 8 USC 1304 – Forms for Registration and Fingerprinting If a federal immigration agent asks for your papers, you must show them. Local and state police are not immigration agents, and you are not required to show foreign identity documents to them during a routine encounter.
Never give false information or present fraudulent documents. Knowingly using another person’s identification in connection with unlawful activity carries up to five years in prison under federal law, and for a noncitizen a conviction for fraud or misrepresentation can independently trigger deportation and bar future legal immigration.10Office of the Law Revision Counsel. 18 U.S. Code 1028 – Fraud and Related Activity in Connection with Identification Documents, Authentication Features, and Information Silence is the safer response.
If You Believe Your Rights Were Violated
If local police stop you solely because of your perceived race, ethnicity, or national origin, or if a jail holds you past your release date based only on an ICE request with no judicial warrant, you may have a federal civil rights claim under 42 U.S.C. § 1983. To prevail, you need to show that someone acting in an official law enforcement capacity deprived you of a constitutional right. Federal courts have allowed monetary damages against localities for holding people on ICE detainers without judicial authorization, and in some of those cases the usual qualified immunity defense did not apply.
The Department of Justice’s 2023 guidance prohibits federal law enforcement from using race, ethnicity, or national origin in enforcement decisions except when tied to a specific suspect description or a credible, detailed tip.11Justice.gov. Guidance for Federal Law Enforcement Agencies Regarding the Use of Race, Ethnicity, Gender, National Origin, Religion, Sexual Orientation, Gender Identity, and Disability That guidance covers federal agents, including those operating in 287(g) partnerships, and expressly bars reliance on generalized stereotypes or pretexts. If you think your rights were violated during an encounter involving immigration enforcement, document the interaction in detail and talk to an immigration attorney or civil rights organization as soon as you can.