Federal vs. State Immigration Laws: Who Has Authority?

Under the U.S. Constitution, federal versus state immigration laws are not an even split: the federal government holds primary authority over who enters the country, who can become a citizen, and who faces removal, while states play a narrower role centered on cooperating with federal enforcement and regulating areas like public benefits and professional licensing. When the two collide, the Supremacy Clause in Article VI settles the dispute in favor of federal law.¹

The word “immigration” does not actually appear in the Constitution. Congress draws its authority from Article I, Section 8, which grants the power to “establish an uniform Rule of Naturalization,” together with the power to regulate commerce with foreign nations and inherent sovereign authority over foreign affairs and borders.²³ The Supreme Court has long described this combined authority as “plenary,” meaning nearly absolute. One national policy governs the entire country rather than fifty separate systems.

What Only the Federal Government Can Decide

Several core immigration functions are exclusively federal, and no state legislature can replicate or modify them.

Congress alone sets the requirements for naturalization. An applicant generally must have been a lawful permanent resident for at least five years, demonstrate good moral character, and meet residency and physical-presence requirements, among other conditions in federal statute.⁴ States cannot create their own paths to citizenship.

The federal government also has exclusive control over visa categories, deciding which foreign nationals qualify for admission and on what terms. Removal proceedings are entirely federal as well: only federal immigration judges, operating within the Department of Justice, can order someone removed, and Congress defines the grounds that trigger removal.⁵

Citizenship itself is federal. The Fourteenth Amendment declares that all persons born or naturalized in the United States, and subject to its jurisdiction, are citizens of the United States and of the state where they reside.⁶ No state can redefine who qualifies.

How Courts Decide Who Wins When Laws Conflict

The doctrine that resolves clashes between federal and state immigration laws is preemption, which flows directly from the Supremacy Clause. Courts look at whether Congress intended to displace state law, and the analysis falls into three categories.

Express preemption applies when Congress writes explicit language forbidding state laws in an area. The clearest immigration example is the employer-sanctions provision of the Immigration Reform and Control Act, which preempts state civil or criminal penalties for hiring unauthorized workers, with a carve-out for “licensing and similar laws.”⁷

Field preemption applies when federal regulation is so comprehensive that Congress clearly intended to occupy the entire field. Alien registration is the classic example; states cannot layer their own registration requirements on top.

Conflict preemption applies when a state law makes compliance with both federal and state law impossible, or creates an obstacle to what Congress was trying to achieve.

The 2012 decision in Arizona v. United States shows how these categories work in practice. The Supreme Court struck down three provisions of Arizona’s S.B. 1070: a state misdemeanor for failing to carry federal registration documents (field preemption over the federal registration scheme), a state criminal penalty on unauthorized workers for seeking work (conflict with Congress’s deliberate choice not to criminalize the worker side of the employer-sanctions framework), and a grant of warrantless arrest authority to state officers based on probable cause of removability (obstacle to federal discretion over removal). The Court upheld a fourth provision requiring officers to check immigration status during lawful stops when they had reasonable suspicion of unlawful presence, treating it as cooperation with the existing federal verification system rather than independent state enforcement.⁸

A year earlier, in Chamber of Commerce v. Whiting, the Court upheld Arizona’s Legal Workers Act, which required suspension or revocation of business licenses for employers who knowingly hired unauthorized workers. That penalty fell within the express “licensing and similar laws” carve-out in federal employer-sanctions law.⁹ Together, the two cases mark the outer edges of state power over the employment side of immigration: states can hit employers through licensing, but they cannot criminalize the workers themselves or invent parallel enforcement schemes.

Where States Do Have Room to Act

Cooperative Enforcement

Federal law authorizes the Attorney General to enter written agreements with state and local governments under which trained officers perform specified immigration functions, including investigating, apprehending, and detaining individuals in the country without authorization.¹⁰ These 287(g) agreements come in several forms, including a jail enforcement model that identifies removable individuals already in custody and a task force model that flags immigration issues during routine police work.¹¹

The important point is that 287(g) authority is delegated federal power, not independent state authority. Officers work under ICE training, direction, and supervision. Outside the scope of the agreement, a state officer has no more immigration authority than any other state employee.

Employment Verification

E-Verify is a federal internet-based system that lets employers check whether new hires are authorized to work. Roughly two dozen states require some or all employers to use it, particularly on state contracts. These mandates are generally permissible because they reinforce the federal verification framework rather than create independent enforcement.

Driver’s Licenses and REAL ID

Driver’s licenses are state-issued, but the REAL ID Act of 2005 imposes minimum standards on licenses used for federal purposes. Applicants for a compliant license must prove identity and immigration status, and as of May 2025 travelers need a REAL ID-compliant license or another acceptable form of identification to board domestic flights and access certain federal facilities.¹² States are not required to issue REAL ID-compliant licenses exclusively. Many operate a two-tier system, and some issue standard, non-compliant licenses to residents regardless of immigration status, which is permissible as long as those licenses are clearly marked.

Professional Licensing

Federal law classifies professional licenses as a “state or local public benefit,” which by default makes them unavailable to individuals without lawful immigration status. The statute includes an override: a state may extend eligibility to individuals without lawful status if the state legislature passes a law affirmatively providing for it after August 22, 1996.¹³ A growing number of states have exercised this option for occupations like law, medicine, and teaching. A state agency cannot do this on its own; the legislature must act explicitly.

Public Benefits

The same statute sets a baseline: individuals who are not “qualified aliens,” certain nonimmigrants, or parolees admitted for at least one year are generally ineligible for state and local public benefits.¹³ The term is broad, covering grants, loans, professional licenses, housing assistance, postsecondary education benefits, food assistance, and unemployment benefits.

Four categories are exempt from that default regardless of immigration status:

Emergency medical care
Emergency disaster relief (short-term, non-cash, in-kind)
Public health services such as immunizations and testing or treatment for communicable diseases
Community services like soup kitchens, crisis counseling, and short-term shelter necessary for the protection of life or safety

Beyond those exceptions, a state legislature can affirmatively extend any benefit to individuals without lawful status, but only through post-1996 legislation.¹³

The Floor States Cannot Fall Below

State authority over benefits has a constitutional floor set by Plyler v. Doe in 1982. The Supreme Court struck down a Texas law that denied state education funding for children who had not been legally admitted, holding that the law violated the Equal Protection Clause of the Fourteenth Amendment. Punishing children for their parents’ immigration decisions bore no rational relationship to a legitimate state interest.¹⁴ Every state must provide free public K-12 education to all children within its borders, regardless of immigration status. Combined with the emergency-benefit exceptions, this creates a set of protections states cannot go below.

Sanctuary Policies and the Limit on Federal Power

The reverse question, how far the federal government can push states into helping, has its own well-established answer. Federal law prohibits state or local governments from restricting their employees from sharing immigration-status information with federal authorities. The statute bars any official from “prohibit[ing], or in any way restrict[ing]” the sending, receiving, maintaining, or exchanging of information about any individual’s citizenship or immigration status.¹⁵ A city cannot order its police to refuse to tell ICE whether someone in custody is a citizen.

What the statute does not do is equally important. It governs information, not active enforcement. A local government can share information and still decline to hold individuals past their release date at ICE’s request, decline to help with immigration raids, and decline to sign a 287(g) agreement.

The constitutional principle behind that space is the anti-commandeering doctrine, established most clearly in Printz v. United States. The Supreme Court struck down a federal law that required local law enforcement to conduct background checks on gun buyers, holding that the Tenth Amendment forbids Congress from commandeering state officers to administer federal regulatory schemes.¹⁶ Applied to immigration, Congress can invite state cooperation and offer incentives, but it cannot order local police to enforce federal immigration law. Federal attempts to condition grant funding on cooperation continue to be litigated under this doctrine and under the constitutional limits on Congress’s spending power.

A Shifting Line

The division of immigration authority is not a fixed boundary. Some states push to be more restrictive than federal enforcement priorities, passing laws that echo federal immigration crimes. Others push the other way, extending benefits and protections to residents regardless of status. Both approaches face the same legal test: whether the state has intruded into territory the Constitution and federal statute reserve for Congress and the executive branch. States have real but bounded authority. They can cooperate with federal enforcement, regulate their own licensing and benefit systems within federal constraints, and choose how much of their own resources to commit. What they cannot do is set independent immigration policy, invent new immigration crimes, or override federal enforcement priorities.

1
Legal Information Institute. Article VI, U.S. Constitution
2
Legal Information Institute. Naturalization Power: Overview
3
Legal Information Institute. Overview of Congress’s Immigration Powers
4
Office of the Law Revision Counsel. 8 USC 1427 – Requirements of Naturalization
5
Legal Information Institute. Naturalization Power
6
Library of Congress. U.S. Constitution – Fourteenth Amendment
7
Office of the Law Revision Counsel. 8 U.S. Code 1324a – Unlawful Employment of Aliens
8
Justia U.S. Supreme Court Center. Arizona v. United States, 567 U.S. 387 (2012)
9
Justia U.S. Supreme Court Center. Chamber of Commerce v. Whiting, 563 U.S. 582 (2011)
10
Office of the Law Revision Counsel. 8 USC 1357 – Powers of Immigration Officers and Employees
11
U.S. Immigration and Customs Enforcement. Partner With ICE Through the 287(g) Program
12
Transportation Security Administration. REAL ID
13
Office of the Law Revision Counsel. 8 USC 1621 – Aliens Who Are Not Qualified Aliens or Nonimmigrants Ineligible for State and Local Public Benefits
14
Justia U.S. Supreme Court Center. Plyler v. Doe, 457 U.S. 202 (1982)
15
Office of the Law Revision Counsel. 8 U.S. Code 1373 – Communication Between Government Agencies and the Immigration and Naturalization Service
16
Justia U.S. Supreme Court Center. Printz v. United States, 521 U.S. 898 (1997)