Texas SB 4 and State Immigration Enforcement: Federal Preemption, Arrest Powers, and the Supremacy Clause

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Texas SB 4 and State Immigration Enforcement: Federal Preemption, Arrest Powers, and the Supremacy Clause

Texas Senate Bill 4, commonly known as SB 4, represents one of the most significant recent attempts by a state to create its own criminal-enforcement mechanism for unauthorized immigration-related conduct. Enacted in 2023, the law creates Texas offenses for certain forms of unauthorized entry and reentry and establishes procedures under which state judges may order certain noncitizens to return to the foreign nation from which they entered or attempted to enter Texas.

The controversy surrounding SB 4 raises a fundamental constitutional question: How far may a state go in enforcing immigration-related conduct when immigration is governed extensively by federal law?

The answer is not simply that states have no authority whenever immigration is involved. The Supreme Court has recognized that states retain substantial police powers and that not every state law concerning noncitizens is automatically preempted. At the same time, federal immigration law occupies a field of extraordinary national importance, and state laws may be displaced when they conflict with federal law or interfere with federal objectives.

SB 4 therefore presents a particularly important federalism problem. Texas has created state criminal offenses that closely track federal immigration offenses, but the state law also establishes its own enforcement procedures and a state-controlled mechanism for ordering a noncitizen to return to a foreign nation.

The resulting dispute concerns the Supremacy Clause, federal preemption, state police powers, the constitutional allocation of immigration authority, Article I’s “invasion” provision, and the procedural requirements of Article III standing.

The litigation has also demonstrated an important lesson in constitutional adjudication: a court may vacate an injunction without deciding whether the challenged law is ultimately constitutional.

As of 2026, that distinction is essential to understanding SB 4.

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Key Takeaways

• SB 4 is a Texas state law, not a federal immigration statute. It creates Texas criminal offenses concerning certain unauthorized entry and reentry into the state.
• The law tracks portions of federal immigration law but does more than simply reproduce federal offenses. It also creates state procedures for arrest, prosecution, and orders requiring certain individuals to return to the foreign nation from which they entered or attempted to enter Texas.
• Federal immigration authority is extensive but does not automatically invalidate every state law involving noncitizens. The central constitutional doctrine is federal preemption.
• Arizona v. United States is the leading modern Supreme Court precedent on state immigration enforcement. The Court held several provisions of Arizona’s SB 1070 preempted while allowing another provision to remain in effect subject to further judicial review.
• SB 4’s current legal status must be distinguished from the merits of its constitutionality. In April 2026, the en banc Fifth Circuit vacated a preliminary injunction because the plaintiffs lacked Article III standing; the majority expressly declined to decide the underlying preemption questions.
• The Fifth Circuit’s 2026 decision therefore did not hold that SB 4 is constitutional. It resolved the particular challenge on jurisdictional standing grounds.
• The “invasion” argument is constitutionally significant but does not by itself settle the preemption question. Texas has relied on Article I, Section 10, Clause 3, while opponents dispute whether large-scale unauthorized migration qualifies as an “invasion” within the constitutional provision.
• State and federal immigration enforcement can coexist in some circumstances. Federal law itself authorizes certain cooperation by state and local officers under specified conditions, demonstrating that the constitutional question is more nuanced than a simple federal-versus-state division.
• SB 4 illustrates the difference between immigration regulation and ordinary state criminal law. A state may generally regulate conduct within its territory, but it cannot use ordinary police powers to accomplish objectives that federal law preempts.

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1. What Is Texas SB 4?

Texas SB 4 was enacted during the state’s 2023 legislative session as part of a broader state response to unauthorized migration across the Texas-Mexico border.

The enacted legislation added Chapter 51 to the Texas Penal Code, titled “Illegal Entry Into This State,” and created related procedures in the Texas Code of Criminal Procedure.

The law establishes two principal immigration-related offenses.

The first concerns illegal entry from a foreign nation. Under Texas Penal Code § 51.02, an “alien” commits an offense if the person enters or attempts to enter Texas directly from a foreign nation at a location other than a lawful port of entry.

The second concerns illegal reentry by certain aliens. Texas Penal Code § 51.03 applies to an alien who enters, attempts to enter, or is found in Texas after having previously been denied admission, excluded, deported, or removed from the United States, or after departing while an exclusion, deportation, or removal order remained outstanding.

The statute therefore creates a state criminal framework that closely parallels federal criminal provisions concerning unlawful entry and reentry.

The Texas Legislature’s enacted text also provides several affirmative defenses tied to federal immigration circumstances, including certain forms of lawful presence, asylum, and specified DACA approvals.

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2. What Powers Does SB 4 Give State Authorities?

The controversy over SB 4 is not limited to the creation of criminal offenses.

The law also establishes procedures through which state judges may issue an order to return to a foreign nation.

Under Article 5B.002 of the Texas Code of Criminal Procedure, a magistrate may, after determining that probable cause exists for an SB 4 offense, release the person from custody and issue an order requiring the person to return to the foreign nation from which the person entered or attempted to enter.

A judge may also issue such an order in lieu of continuing the prosecution under specified circumstances.

The statute imposes conditions on such an order. Among other things, the person must agree to the order in the circumstances covered by the discharge mechanism, must not have previously been convicted of an applicable Chapter 51 offense or received a previous discharge under the provision, and must not be charged with another sufficiently serious offense. The arresting agency must also collect identifying information and cross-reference relevant databases.

For a person convicted of an SB 4 offense, the statute directs the judge to enter an order requiring the person to return to the foreign nation from which the person entered or attempted to enter. That order takes effect after completion of the applicable term of confinement.

The statute also creates an offense for refusing to comply with an applicable return order.

These provisions are constitutionally significant because removal from the United States is ordinarily administered through the federal immigration system.

The central legal question is therefore not simply whether Texas may punish conduct occurring within Texas. It is whether Texas may create a state system whose operation overlaps with — and potentially conflicts with — the federal government’s authority over admission, removal, and immigration status.

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3. SB 4 and the Federal Immigration System

The federal government regulates immigration principally through the Immigration and Nationality Act (INA) and related federal statutes and regulations.

Federal immigration law addresses matters including:

• admission into the United States;
• inspection at ports of entry;
• inadmissibility;
• lawful immigration status;
• asylum;
• removal;
• deportation;
• reentry after removal;
• immigration detention;
• parole;
• visas;
• naturalization; and
• numerous forms of humanitarian protection.

Federal law also establishes institutions responsible for administering these rules, including the Department of Homeland Security, U.S. Citizenship and Immigration Services, Customs and Border Protection, Immigration and Customs Enforcement, the Department of State, and the Department of Justice’s immigration courts and Board of Immigration Appeals.

This comprehensive federal structure matters because immigration status can involve complicated federal determinations.

A person encountered inside Texas may not simply be “illegal” or “legal” in the simplistic sense sometimes suggested in political discussion. The person may be:

• an applicant for admission;
• an asylum applicant;
• a parolee;
• a lawful permanent resident;
• a person with temporary protected status;
• a person subject to a removal order;
• a person eligible for federal relief;
• a person whose federal status is unresolved; or
• a person falling into another category established by federal law.

A state criminal statute operating against those individuals therefore potentially interacts with federal determinations that Texas itself does not control.

That interaction lies at the heart of the preemption dispute.

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4. The Supremacy Clause and Federal Preemption

The Supremacy Clause, Article VI, Clause 2 of the Constitution, establishes federal law as the supreme law of the land.

The Clause forms the constitutional basis for federal preemption.

Federal preemption can occur in several forms, including:

• express preemption, when Congress expressly displaces state law;
• field preemption, when federal regulation is so comprehensive or the federal interest so dominant that state regulation is displaced; and
• conflict preemption, when state law conflicts with federal law.

Conflict preemption includes situations in which compliance with both federal and state law is impossible and situations in which state law presents an obstacle to the accomplishment and execution of federal objectives.

The Cornell Legal Information Institute’s explanation of federal preemption describes these categories and emphasizes that the existence of federal regulation does not automatically mean that every state law touching the same subject is preempted.

That qualification is particularly important in immigration law.

The correct legal proposition is not:

“Every state law involving immigrants is unconstitutional.”

Nor is it:

“States may enforce any immigration-related rule because they possess police powers.”

The constitutional analysis depends on the particular state law, the federal statutory framework, the nature of the conflict, and the constitutional interests involved.

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5. Arizona v. United States

The Supreme Court’s principal modern precedent is Arizona v. United States, 567 U.S. 387 (2012).

Arizona had enacted SB 1070, a state law containing several provisions concerning unauthorized immigration.

The Supreme Court invalidated three provisions as preempted by federal law while declining to invalidate another provision at the preliminary stage without further consideration of how it would be construed and applied.

The decision is important for two reasons.

First, the Court recognized the federal government’s significant authority over immigration.

Second, the Court did not adopt a rule that every state law touching immigration is automatically invalid.

Instead, the Court examined each provision in relation to the federal statutory scheme.

This is why Arizona is relevant to SB 4 but does not mechanically answer the case.

The precise question is whether the particular provisions of SB 4 are displaced by federal law under the applicable preemption doctrine.

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6. Field Preemption and Immigration

One possible argument against SB 4 is that Congress has occupied the field of immigration enforcement so extensively that states cannot create their own parallel system governing entry and removal.

Field preemption is particularly significant in areas involving strong national interests.

The Supreme Court has recognized that immigration is closely connected to national sovereignty and foreign relations. The federal government must be capable of speaking for the United States in dealings with foreign nations and of administering a national immigration system.

The Constitution therefore creates an especially powerful federal interest in immigration.

Nevertheless, field preemption must be applied carefully.

The Supreme Court’s cases do not establish that every state law touching noncitizens is categorically preempted. Indeed, Arizona itself demonstrates that different state provisions can receive different treatment.

The question is therefore whether the particular subject regulated by SB 4 falls within an area in which Congress has displaced state authority.

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7. Conflict and Obstacle Preemption

The more immediate controversy surrounding SB 4 concerns conflict preemption.

A state law can be preempted when it interferes with the operation or objectives of federal law even if it does not directly contradict a federal statute word for word.

This becomes important when comparing the Texas scheme with federal immigration enforcement.

Federal immigration law gives federal officials substantial authority and discretion concerning:

• whether to initiate removal proceedings;
• whom to prioritize;
• whether to pursue criminal prosecution;
• whether to pursue civil immigration proceedings;
• whether to grant certain forms of relief;
• whether to permit a person to remain temporarily;
• and how to execute removal orders.

SB 4 establishes a state criminal mechanism that can operate independently of those federal choices.

That creates the constitutional question:

Can Texas impose its own mandatory criminal and return-order consequences when federal officials may have made — or may later make — a different immigration determination?

That is a classic obstacle-preemption question.

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8. Similarity to Federal Law Does Not Necessarily Resolve the Issue

Texas has emphasized that SB 4 closely tracks federal criminal statutes concerning unlawful entry and reentry.

That similarity is legally significant, but it does not automatically resolve the preemption question.

A state law can sometimes coexist with federal law even when the two regulate related conduct.

At the same time, merely copying federal language does not necessarily give a state authority that the Constitution or Congress has withheld.

The more important question is what happens after the state creates its offense.

Federal immigration law does not simply define unlawful entry. It also establishes procedures for inspection, admission, removal, asylum, humanitarian protection, prosecution, and executive discretion.

Thus, two statutes can use similar words while operating within substantially different legal systems.

SB 4’s opponents argue that its consequences, particularly its state-controlled return mechanism, interfere with federal decisions that Congress assigned to federal authorities.

Texas argues that the state is enforcing its own criminal law rather than exercising federal immigration authority.

The distinction between those positions is central to the constitutional litigation.

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9. State Police Powers

States possess broad authority to enact criminal laws protecting public safety within their territories.

That authority includes laws concerning:

• trespass;
• assault;
• trafficking;
• theft;
• fraud;
• drug offenses;
• violence; and
• numerous other forms of conduct.

A state does not lose its ordinary police powers merely because the person committing the offense happens to be a noncitizen.

The constitutional difficulty arises when the state law is directed toward a subject that federal law has reserved to the federal government or when the state law conflicts with federal objectives.

This distinction is essential.

For example, a state may prosecute a noncitizen for an ordinary state criminal offense without necessarily exercising an immigration power.

But if a state creates a legal regime whose central purpose and operation are to determine who may enter the United States, who may remain in the country, or who must be removed to another nation, the federalism question becomes much more serious.

SB 4 sits directly at that boundary.

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10. State Officers and Federal Immigration Enforcement

The constitutional analysis is also complicated by the fact that federal law itself permits certain cooperation between federal immigration authorities and state or local officers.

Under 8 U.S.C. § 1357(g), qualifying state and local officers may perform certain immigration-enforcement functions under agreements with the federal government and subject to federal direction and supervision.

That statutory framework demonstrates that federal exclusivity does not necessarily mean that state officers can never participate in immigration enforcement.

But cooperation under federal authorization is different from a state independently creating its own immigration enforcement system.

This distinction is important when evaluating SB 4.

The question is not simply whether a Texas officer may ever arrest a noncitizen in connection with immigration enforcement.

The question is what legal authority permits the arrest, what offense is being enforced, what federal supervision exists, and what happens after the arrest.

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11. The “Invasion” Argument

Texas has also invoked Article I, Section 10, Clause 3 of the Constitution.

That provision states that a state may not “engage in War” unless actually invaded or in such imminent danger that delay cannot be permitted.

Texas has argued that the extraordinary circumstances at the southern border justify state action under the constitutional concept of invasion.

This argument presents a separate constitutional question from preemption.

The provision does not expressly mention immigration. Nor does it establish a general state power to enforce immigration laws whenever a state considers federal border policy inadequate.

The difficult question is therefore one of constitutional interpretation:

What constitutes an “invasion” for purposes of Article I, Section 10?

The traditional understanding of the term has been associated with military or armed incursions. Whether and to what extent the term could encompass large-scale unlawful migration is deeply contested.

The 2026 Fifth Circuit litigation did not produce a definitive judicial resolution of that question.

Indeed, the en banc majority resolved the case on standing grounds without reaching the preemption merits.

Accordingly, the “invasion” theory should be presented as an argument advanced by Texas, not as an established constitutional exception permitting states to enforce immigration law independently.

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12. Due Process and Immigration Proceedings

SB 4 also raises questions concerning procedural protections.

Federal immigration proceedings can involve complicated determinations concerning:

• asylum;
• withholding of removal;
• protection under the Convention Against Torture;
• lawful status;
• family relationships;
• prior removal orders;
• criminal history;
• and other statutory forms of relief.

A state criminal proceeding operates under a different legal framework.

That difference matters because a state judge applying SB 4 is not simply performing the same adjudicatory function as a federal immigration judge.

The question therefore becomes whether a state criminal proceeding can lawfully produce consequences that effectively determine whether a person leaves the United States, particularly when federal immigration proceedings or applications are pending.

This is one of the strongest reasons why SB 4 implicates more than ordinary state criminal law.

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13. Risk of Unequal or Arbitrary Enforcement

SB 4 also raises practical constitutional questions concerning enforcement.

A statute that authorizes state officers to arrest people for immigration-related offenses inevitably requires officers to determine whether the statutory conditions are satisfied.

That can involve questions about:

• where a person entered;
• whether the person entered from a foreign nation;
• whether the person crossed at a lawful port of entry;
• whether the person has previously been removed;
• whether a federal immigration determination affects the case;
• and whether a statutory defense applies.

Critics of SB 4 have argued that these enforcement powers could encourage discriminatory stops or arrests based on race, ethnicity, language, or perceived national origin.

Such concerns do not automatically establish a constitutional violation. Constitutional claims concerning discriminatory enforcement require application of the relevant legal standards to the particular facts.

Nevertheless, enforcement discretion is an important practical consideration whenever a state creates a criminal offense that depends on immigration status or circumstances of entry.

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14. Diplomatic and Foreign-Relations Concerns

Another distinctive feature of SB 4 is its return-order mechanism.

The statute contemplates requiring a person to return to the foreign nation from which the person entered or attempted to enter Texas.

That creates an obvious international dimension.

Ordinarily, the federal government represents the United States in relations with foreign states.

Immigration enforcement can therefore affect more than domestic criminal law. It can involve questions of:

• repatriation;
• diplomatic relations;
• international obligations;
• asylum;
• protection from persecution;
• and agreements concerning the acceptance of returned nationals.

This helps explain why the Supreme Court has historically treated immigration as an area involving substantial national interests.

A state that orders a person to leave the United States and return to another country is potentially exercising authority with consequences extending beyond the state’s own territory.

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15. The Litigation Over SB 4

SB 4 was challenged before it could take effect.

The litigation initially produced a preliminary injunction in the U.S. District Court for the Western District of Texas. The district court concluded that the plaintiffs had standing and that SB 4 was likely preempted by federal immigration law.

The case then moved through the Fifth Circuit.

A Fifth Circuit panel later affirmed the preliminary injunction in 2025. That panel decision was subsequently vacated when the Fifth Circuit agreed to rehear the case en banc.

The procedural history then changed significantly.

After the federal government changed position and withdrew its claims in 2025, the remaining plaintiffs included immigration-advocacy organizations and El Paso County.

The en banc Fifth Circuit reconsidered whether those plaintiffs had Article III standing.

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16. The Fifth Circuit’s April 2026 Decision

On April 24, 2026, the en banc Fifth Circuit vacated the preliminary injunction.

The majority held that the remaining plaintiffs lacked Article III standing.

This is a crucial distinction.

The court did not hold:

“SB 4 is constitutional.”

Nor did it hold:

“SB 4 is not preempted by federal immigration law.”

Instead, the majority concluded that the plaintiffs had not demonstrated the type of concrete injury required to bring the challenge in federal court. Because the plaintiffs lacked standing, the court did not reach the underlying preemption merits.

The majority specifically rejected theories based on organizations voluntarily diverting resources to respond to the law and rejected El Paso County’s theories of reputational injury and speculative future costs.

The result was that the preliminary injunction was vacated.

That means the earlier judicial barrier to enforcement was removed.

But the constitutional questions surrounding SB 4 were not definitively resolved by that decision.

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17. Why the 2026 Decision Does Not Settle SB 4’s Constitutionality

The distinction between jurisdiction and merits is fundamental to understanding the case.

Article III standing asks whether a particular plaintiff has suffered a sufficient injury to invoke the jurisdiction of a federal court.

Preemption, by contrast, asks whether the state law is displaced by federal law.

These are separate questions.

A court can determine:

“These plaintiffs cannot bring this case.”

without determining:

“The challenged statute is valid.”

The Fifth Circuit’s 2026 decision illustrates exactly that situation.

The majority expressly declined to reach the preemption question because the standing defect was dispositive.

This is why descriptions of the decision as a judicial determination that SB 4 “survived constitutional scrutiny” would be inaccurate.

The law became enforceable after the injunction was vacated, but the merits of the preemption dispute remained unresolved in that litigation.

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18. The Dissents and the Unresolved Merits

The en banc decision also produced substantial disagreement among the judges.

Several judges dissented from the majority’s standing analysis.

Some of the dissenting opinions went further and addressed the underlying preemption question.

Those opinions argued that SB 4 conflicts with the federal immigration framework, including federal control over admission, removal, and immigration enforcement discretion.

Other judges took a different view and argued that the state law should not be treated as categorically preempted merely because it operates in an area touching immigration.

The existence of these sharply divided opinions is significant, but dissenting opinions are not controlling law.

They demonstrate the unresolved nature of the constitutional debate rather than establishing the governing rule.

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19. Why SB 4 Is Different From Arizona SB 1070

SB 4 is frequently compared with Arizona’s SB 1070.

The comparison is appropriate because both laws involve state attempts to address unauthorized immigration.

But the statutes are not identical.

Arizona v. United States involved several distinct provisions, and the Supreme Court analyzed each separately.

SB 4 creates its own criminal offenses and, importantly, its own return-order mechanism.

The constitutional analysis therefore cannot simply be:

“The Supreme Court struck down Arizona’s law, so SB 4 must also be unconstitutional.”

Nor can it be:

“Arizona had one provision survive, so SB 4 is automatically permissible.”

The Supreme Court’s methodology in Arizona requires attention to the precise relationship between state law and the federal immigration framework.

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20. Federalism and the Risk of a Patchwork Immigration System

One of the deepest structural concerns raised by SB 4 is the possibility of different state immigration-enforcement systems developing across the country.

Imagine that several states adopted different definitions of unauthorized entry, different penalties, different detention rules, and different procedures for removing people from their territories.

A person could then face substantially different consequences depending on which state he or she entered.

Immigration, however, necessarily has an interstate and international dimension.

A person admitted to the United States by the federal government does not ordinarily receive a different federal immigration status simply because that person crosses from one state to another.

This national characteristic is one reason federal uniformity is so important.

At the same time, federalism permits states to retain significant authority over matters within their territory.

The constitutional challenge is therefore one of boundary drawing, not simply state-versus-federal authority.

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21. Civil Rights and Enforcement Concerns

The practical operation of SB 4 also raises questions about how immigration-related state offenses will be enforced.

Critics have warned that immigration-related enforcement can create risks of:

• racial profiling;
• mistaken arrests;
• interference with federal immigration proceedings;
• reluctance to report crimes;
• reduced cooperation with police;
• and unequal treatment of individuals based on perceived immigration status.

These concerns must be separated from the legal question of whether the statute is facially preempted.

A law can raise serious enforcement concerns without every enforcement action necessarily violating the Constitution.

Conversely, a statute can be challenged on constitutional grounds even before discriminatory enforcement has been demonstrated in a particular case.

The distinction between facial challenges and as-applied challenges is therefore important to understanding future litigation involving SB 4.

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22. Administrative and Institutional Consequences

SB 4 also creates practical consequences for the institutions responsible for enforcing it.

Texas law enforcement agencies may have to determine whether conduct falls within the state offenses, while courts must process prosecutions and potential return orders.

At the same time, federal immigration authorities operate under a separate statutory system.

This can create questions concerning:

• information sharing;
• detention;
• federal immigration holds;
• pending asylum applications;
• existing removal orders;
• federal prosecutorial discretion;
• transportation;
• identification;
• and coordination between state and federal agencies.

The existence of cooperation mechanisms does not eliminate the constitutional issue.

Indeed, the more extensively the state system interacts with federal immigration decisions, the more important the allocation of authority becomes.

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23. SB 4 and the Meaning of “State Sovereignty”

The political debate surrounding SB 4 often uses the language of state sovereignty.

But constitutional federalism does not mean that every governmental power is divided into completely separate spheres.

States possess sovereignty within the constitutional system, but the Constitution also creates national powers that bind the states.

The Supremacy Clause is one of the principal mechanisms through which federal law takes precedence over conflicting state law.

Thus, the legal question is not whether Texas is sovereign.

Texas unquestionably possesses governmental authority.

The question is whether the particular authority asserted by Texas is compatible with federal law and the Constitution.

That is a much narrower and more legally precise question.

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24. What SB 4 Means for the Future of State Immigration Enforcement

SB 4 could become an important precedent even if the ultimate constitutional questions remain unresolved.

If states can create independent criminal penalties for unauthorized entry and reentry and establish their own removal mechanisms, the traditional division between federal immigration enforcement and state criminal law could change substantially.

Other states could attempt similar legislation.

If courts instead conclude that such laws are preempted, SB 4 could become an important reaffirmation of federal supremacy in immigration.

The ultimate significance therefore extends beyond Texas.

The case concerns the constitutional limits of state experimentation in an area that has traditionally been dominated by federal law.

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25. A More Precise Understanding of the “Right to Arrest”

The phrase “right to arrest” can itself be misleading.

SB 4 does not create an unlimited state authority to arrest anyone whom an officer believes is unlawfully present in the United States.

The statute establishes particular Texas offenses with defined elements.

The constitutional controversy concerns whether Texas may create and enforce those offenses in the first place and whether the resulting state procedures interfere with federal immigration authority.

The relevant legal question is therefore not:

“Can Texas police arrest immigrants?”

It is:

“Can Texas create state criminal offenses based on specified immigration-related conduct and enforce those offenses independently of the federal immigration system?”

That formulation captures the real constitutional issue much more accurately.

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26. The Central Constitutional Question

SB 4 ultimately presents a conflict between two powerful principles.

On one side is the state’s authority to protect public safety and enforce criminal laws within its borders.

On the other is the federal government’s constitutional and statutory authority to maintain a coherent national immigration system.

Neither principle can simply be ignored.

The Supreme Court’s preemption doctrine attempts to determine where the boundary lies.

Arizona v. United States establishes that states cannot interfere with federal immigration objectives merely by characterizing their laws as ordinary state criminal regulations. At the same time, the Supreme Court has not held that every state law affecting noncitizens is automatically preempted.

SB 4 therefore presents a particularly difficult application of federalism principles because it combines a state criminal statute with a mechanism that can produce immigration-related consequences.

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Conclusion

Texas SB 4 represents one of the most consequential modern experiments in state immigration enforcement.

The law creates Texas offenses for certain forms of unauthorized entry and reentry and establishes a state judicial mechanism for ordering certain noncitizens to return to the foreign nation from which they entered or attempted to enter Texas.

Its constitutional significance lies in the interaction between those state powers and the federal immigration system.

The central legal doctrines include federal preemption, the Supremacy Clause, state police powers, federal control over immigration, Article III standing, and the constitutional allocation of authority between the states and the national government.

The Supreme Court’s decision in Arizona v. United States provides an important framework for analyzing state immigration laws, but it does not automatically determine SB 4’s validity.

The litigation surrounding SB 4 has also produced an important procedural lesson. In April 2026, the en banc Fifth Circuit vacated the preliminary injunction because the plaintiffs lacked Article III standing. The court therefore did not decide whether SB 4 is preempted by federal immigration law.

Consequently, the current legal position must be described carefully: SB 4 is no longer blocked by the preliminary injunction that previously prevented its enforcement, but the Fifth Circuit’s April 2026 decision did not resolve the ultimate merits of the statute’s federal-preemption challenge.

That distinction is essential.

SB 4 therefore remains an important constitutional case study in the limits of state power. It asks whether a state may respond to perceived failures in federal immigration enforcement by creating its own criminal and removal-related mechanisms — and, more broadly, how American federalism should operate when state interests, federal immigration authority, and international consequences converge.

The enduring significance of SB 4 is not simply whether Texas may enforce one particular statute. It is the larger constitutional question of how far state power can extend into a field in which federal law, national sovereignty, and foreign relations are deeply intertwined.

Frequently Asked Questions

What is Texas SB 4?

SB 4 is a Texas law enacted in 2023 that creates state criminal offenses concerning certain unauthorized entry and reentry and establishes procedures for state judges to issue orders requiring certain individuals to return to the foreign nation from which they entered or attempted to enter Texas.

Does SB 4 give Texas police unlimited immigration-enforcement authority?

No. SB 4 creates specific state offenses and procedures. The constitutional controversy concerns whether Texas has authority to create and enforce those provisions in light of federal immigration law.

Is SB 4 the same as Arizona’s SB 1070?

No. Both laws involve state immigration enforcement, but they contain different provisions. Arizona v. United States is relevant because it establishes important preemption principles, but the constitutionality of SB 4 requires analysis of its own provisions.

What is federal preemption?

Federal preemption is the constitutional doctrine under which federal law can displace conflicting state law. It may occur through express preemption, field preemption, or conflict preemption.

Why is Arizona v. United States important to SB 4?

Arizona is the Supreme Court’s leading modern decision concerning state immigration enforcement. The Court held several provisions of Arizona’s SB 1070 preempted while allowing another provision to proceed subject to further judicial review.

Did the Fifth Circuit rule that SB 4 is constitutional?

No. In April 2026, the en banc Fifth Circuit vacated the preliminary injunction because the plaintiffs lacked Article III standing. The majority did not decide the underlying preemption merits.

Is SB 4 currently blocked by a federal injunction?

The preliminary injunction that had blocked enforcement was vacated by the en banc Fifth Circuit on April 24, 2026. The majority’s decision was based on standing rather than a determination that SB 4 satisfied federal constitutional requirements.

What is the “invasion” argument concerning SB 4?

Texas has argued that the circumstances at the southern border implicate Article I, Section 10, Clause 3 of the Constitution, which addresses state action when a state is “actually invaded” or faces imminent danger. Whether that provision authorizes the type of immigration enforcement contemplated by SB 4 is a contested constitutional question.

Can states participate in federal immigration enforcement?

In some circumstances, yes. Federal law permits certain state and local officers to perform specified immigration-enforcement functions under federal authorization and supervision. That is different from a state independently creating its own immigration-enforcement system.

Why does SB 4 raise foreign-relations concerns?

The statute establishes procedures under which a person may be ordered to return to a foreign nation. Immigration and relations with foreign governments are matters of national concern, which is one reason federal authority has historically played a dominant role in immigration.

Does federal supremacy mean that states cannot regulate noncitizens?

No. Not every state law affecting noncitizens is automatically preempted. The relevant question is whether the particular state law conflicts with federal law or intrudes into an area that federal law has reserved exclusively to the federal government.

Why is the distinction between standing and preemption important?

Standing concerns whether a particular plaintiff has suffered the type of injury required to invoke federal judicial jurisdiction. Preemption concerns whether state law is displaced by federal law. A court can dismiss a challenge for lack of standing without deciding whether the challenged law is constitutional.

Why is SB 4 important beyond Texas?

SB 4 tests the constitutional boundary between state police powers and federal immigration authority. Its legal treatment could influence how other states approach immigration enforcement and how courts apply federal preemption principles to similar state legislation.