What Is U.S. Immigration Law?

What Is U.S. Immigration Law?

U.S. immigration law is the body of federal law governing the entry, admission, presence, employment, protection, removal, and eventual naturalization of people who are not United States citizens or nationals. It also establishes rules concerning visas, lawful permanent residence, asylum and refugee protection, immigration enforcement, citizenship, and the legal relationship between noncitizens and the United States.

Unlike many areas of American law, immigration law is overwhelmingly a matter of federal law. Congress establishes the principal statutory framework, federal agencies administer and enforce that framework, and federal courts interpret the Constitution, statutes, regulations, and other applicable sources of law.

The principal federal statute is the Immigration and Nationality Act (INA), codified primarily in Title 8 of the United States Code. The INA governs a remarkably broad range of immigration matters, from visa classifications and admission requirements to removal proceedings and naturalization.

Immigration law, however, is not simply a collection of visa rules. It is a complex legal system that determines who may enter the United States, under what conditions a person may remain, what rights and obligations accompany different immigration statuses, and under what circumstances the government may require a person to leave the country.

Understanding those foundations is essential before studying more specialized subjects such as visas, lawful permanent residence, asylum, deportation, immigration detention, or naturalization.

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What Does Immigration Law Mean?

In its broadest sense, immigration law concerns the legal movement and residence of people across national borders.

For the United States, this includes questions such as:

• Who may enter the country?
• Who may receive a visa?
• Who may be admitted at the border?
• Who may live permanently in the United States?
• Who may work in the United States?
• Who may study or visit temporarily?
• Who may seek asylum or refugee protection?
• What happens when a person violates the terms of an immigration status?
• When may a person be removed from the United States?
• What protections are available during immigration proceedings?
• How can a lawful permanent resident become a U.S. citizen?
• When can citizenship be acquired or derived without naturalization?

The legal system distinguishes among many different categories of people and statuses.

A person may be a U.S. citizen, a U.S. national who is not a citizen, a lawful permanent resident, a temporary nonimmigrant, an asylee, a refugee, or a person without lawful immigration status, among other classifications.

Cornell’s Legal Information Institute explains that federal immigration law determines the legal status, rights, duties, and obligations associated with noncitizens and also provides mechanisms through which eligible noncitizens may become naturalized citizens.

These distinctions matter because immigration law does not treat every noncitizen in the same way.

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Immigration Law Is Primarily Federal Law

One of the most important characteristics of U.S. immigration law is its federal character.

The Constitution does not contain a single clause stating, in simple terms, “Congress shall regulate immigration.” Instead, the constitutional foundation of federal immigration power has developed through several provisions, principles of national sovereignty, congressional powers, and Supreme Court decisions.

Congress has express constitutional authority to establish a uniform rule of naturalization under Article I, Section 8, Clause 4. Congress also possesses powers involving foreign commerce and foreign affairs, while the federal government’s authority over immigration has historically been understood in connection with national sovereignty.

The Supreme Court has consequently recognized broad federal authority over immigration, particularly concerning the admission and exclusion of foreign nationals.

The U.S. Constitution Annotated explains that the Supreme Court has long recognized substantial congressional power over immigration, although the precise constitutional sources and limits of that power have developed through judicial decisions.

This federal structure is fundamental to understanding why immigration policy cannot ordinarily be established independently by each state.

The United States has one national immigration system rather than fifty separate state immigration systems.

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The Immigration and Nationality Act

The Immigration and Nationality Act, commonly called the INA, is the central statutory foundation of modern U.S. immigration law.

The INA was enacted in 1952 and has been amended many times. Major amendments have changed the structure of family-based immigration, employment-based immigration, refugee and asylum protection, immigration enforcement, naturalization, and other areas.

The INA is codified primarily in Title 8 of the United States Code.

It contains provisions addressing subjects including:

• nationality and citizenship;
• definitions used throughout immigration law;
• immigrant and nonimmigrant classifications;
• visa requirements;
• grounds of inadmissibility;
• inspection and admission;
• lawful permanent residence;
• employment authorization;
• asylum and refugee protection;
• removal and deportation;
• immigration detention;
• immigration-related criminal offenses;
• naturalization; and
• administrative procedures.

The INA should therefore be thought of as the central statutory architecture of U.S. immigration law, rather than as a single set of rules concerning visas.

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Other Federal Immigration Statutes

Although the INA is the central statute, it is not the only federal law relevant to immigration.

Congress has enacted numerous statutes affecting particular aspects of immigration, nationality, border enforcement, employment, criminal law, federal benefits, and administrative procedure.

Other federal laws may therefore become relevant depending upon the legal question involved.

For example, immigration cases may involve:

• the Administrative Procedure Act;
• federal criminal statutes;
• federal civil-rights statutes;
• appropriations laws;
• federal employment statutes;
• laws governing federal agencies;
• international agreements implemented through federal law; and
• specific congressional enactments addressing particular immigration programs.

The result is that immigration law intersects with many other areas of federal law.

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Federal Immigration Regulations

Statutes provide the principal legal framework, but Congress does not administer every immigration program directly.

Federal agencies issue regulations implementing statutes enacted by Congress.

These regulations are published in the Code of Federal Regulations (CFR).

Immigration regulations can govern matters such as:

• visa procedures;
• applications and petitions;
• eligibility requirements;
• employment authorization;
• asylum procedures;
• detention;
• removal proceedings;
• naturalization procedures;
• documentation;
• agency decision-making; and
• administrative appeals and review.

A statute therefore may establish a broad legal requirement while regulations provide the procedural and administrative details necessary to implement it.

Regulations must remain within the authority granted by Congress and must comply with the Constitution and other controlling law.

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Federal Agencies and Immigration Law

No single federal agency controls every aspect of U.S. immigration.

Different responsibilities are divided among several federal institutions.

Department of Homeland Security

The Department of Homeland Security (DHS) administers and enforces major portions of federal immigration law.

Three DHS components are particularly important:

U.S. Citizenship and Immigration Services

USCIS generally handles immigration benefits and applications, including many petitions, applications for lawful permanent residence, employment authorization, asylum applications, and naturalization.

U.S. Customs and Border Protection

CBP is responsible for border security and inspection at ports of entry, including determining whether individuals seeking admission may enter the United States under applicable law.

U.S. Immigration and Customs Enforcement

ICE is responsible for important aspects of immigration enforcement within the United States, including investigations, detention, and removal operations.

These agencies perform different functions even though they operate within the same federal department.

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The Department of State

The Department of State plays a central role in the visa system.

U.S. embassies and consulates abroad process visa applications and conduct consular adjudication.

This creates an important distinction between a visa and admission.

A visa generally allows a person to seek entry to the United States at a port of entry. It does not itself guarantee admission.

When the person arrives, federal immigration officers determine whether the person is admissible and may be admitted under the applicable law.

The distinction between visa issuance and admission becomes particularly important in cases involving inadmissibility, inspection, temporary visas, and immigration status.

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The Department of Justice and Immigration Courts

The Executive Office for Immigration Review (EOIR) operates within the Department of Justice and administers the immigration court system.

Immigration judges decide many removal cases and certain other matters arising under federal immigration law.

The Board of Immigration Appeals (BIA) reviews certain decisions of immigration judges.

This creates another important distinction:

USCIS is not the immigration court system.

USCIS generally adjudicates immigration benefits, while immigration courts and the BIA handle specified matters within the adjudicatory system administered by EOIR.

Federal courts can also become involved, particularly when parties seek judicial review of agency action or raise constitutional and statutory questions within federal judicial jurisdiction.

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The Main Sources of U.S. Immigration Law

A useful way to understand immigration law is to identify its principal legal sources.

1. The U.S. Constitution

The Constitution establishes the structure of federal government and imposes constitutional limits on governmental action.

Constitutional provisions and doctrines relevant to immigration include principles involving:

• federal power;
• separation of powers;
• due process;
• equal protection;
• federalism;
• the Supremacy Clause;
• congressional authority;
• executive authority; and
• judicial review.

The Constitution therefore does two things at once: it provides authority for governmental action and places limits on that authority.

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2. Federal Statutes

Congress creates immigration law primarily through federal statutes.

The INA is the central statute, but other federal statutes can also affect immigration cases.

Federal statutes are especially important because Congress determines the basic legal categories and conditions under which noncitizens may enter, remain, work, seek protection, or become citizens.

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3. Federal Regulations

Agencies implement congressional statutes through regulations.

Regulations can provide detailed procedural and substantive rules, but they cannot lawfully exceed the authority granted by Congress.

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4. Judicial Decisions

Federal courts interpret the Constitution, statutes, regulations, and other legal authorities.

Supreme Court decisions are particularly important because they establish controlling constitutional and statutory interpretations.

Immigration law contains a substantial body of case law concerning:

• federal immigration power;
• preemption;
• due process;
• detention;
• removal;
• judicial review;
• asylum;
• citizenship;
• state regulation of noncitizens; and
• the constitutional rights of people within the United States.

The judicial interpretation of immigration statutes can therefore be as important to understanding the law as the statutory text itself.

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5. Administrative Decisions and Guidance

Immigration agencies also issue policy materials, manuals, decisions, instructions, and other forms of administrative guidance.

These materials can be useful in understanding how agencies administer immigration statutes and regulations.

However, an agency policy manual or internal guidance document should not automatically be treated as equivalent to a statute enacted by Congress or a regulation properly promulgated under federal administrative law.

The legal authority of a particular document depends on what it is, which agency issued it, what statutory authority supports it, and whether it has the force of law.

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Immigration Status and Immigration Classification

One of the first concepts students of immigration law must understand is the difference between status and classification.

Immigration law establishes numerous categories for people who are not U.S. citizens.

Two broad categories are particularly important:

Immigrants

An immigrant generally enters the United States with authorization to reside permanently, subject to the conditions established by law.

A lawful permanent resident, commonly called a green-card holder, is the most familiar example.

Nonimmigrants

Nonimmigrants are admitted for temporary purposes under specific statutory classifications.

Examples include certain visitors, students, temporary workers, diplomats, and other categories established by federal law.

Cornell’s Wex explains that nonimmigrant classifications generally concern temporary travel, study, work, or other specified purposes, while the INA defines the categories and conditions under which those classifications operate.

But these are only broad categories.

Immigration law contains many specialized classifications, each with its own eligibility requirements.

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Immigration Status Is Not the Same as Citizenship

A person may have lawful immigration status without being a U.S. citizen.

For example, a lawful permanent resident can ordinarily live and work permanently in the United States without becoming a citizen.

A nonimmigrant may lawfully remain in the United States for a specified temporary purpose and period without acquiring permanent residence.

An asylee or refugee may have lawful protection under a particular statutory framework without immediately becoming a citizen.

Citizenship is therefore a distinct legal status.

Naturalization is one method by which an eligible noncitizen may acquire citizenship after birth. Citizenship can also arise through other legal mechanisms, including acquisition or derivation under the applicable nationality laws.

Understanding this distinction prevents one of the most common errors in introductory discussions of immigration law: treating every person who is lawfully present as an immigrant and every immigrant as a future citizen.

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Admission, Presence, and Removal

Three concepts provide another useful foundation for immigration law:

admission, presence, and removal.

Admission

Admission concerns the legal process through which a person is permitted to enter the United States after inspection under federal immigration law.

Presence

Once in the United States, a person’s legal relationship with the country depends on the applicable immigration status, classification, authorization, and other circumstances.

Removal

Federal immigration law also establishes procedures through which certain noncitizens may be removed from the United States.

Removal is the modern statutory term generally used for what older sources commonly call “deportation.”

The legal basis for removal is not identical to the legal basis for refusing admission.

This distinction is fundamental.

A person seeking entry may be found inadmissible, while a person already present in the United States may be subject to removability under different statutory provisions.

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Inadmissibility and Removability

The distinction between inadmissibility and removability is one of the most important concepts in U.S. immigration law.

Inadmissibility

The grounds of inadmissibility are principally contained in INA §212, codified at 8 U.S.C. §1182.

They can concern matters such as:

• certain criminal conduct;
• controlled-substance violations;
• fraud or misrepresentation;
• unlawful presence;
• certain health-related grounds;
• security-related grounds;
• public-charge provisions; and
• other statutory grounds.

Removability

The grounds of deportability or removability are principally contained in INA §237, codified at 8 U.S.C. §1227.

They address circumstances in which a noncitizen who has been admitted may become removable under federal law.

The two concepts overlap in subject matter but are not interchangeable.

A proper understanding of immigration law therefore requires careful attention to whether a particular statute concerns admission and inadmissibility or removal and removability.

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Immigration Law and State Governments

Although immigration is primarily federal, states have not disappeared from the legal picture.

States retain substantial authority over matters within their traditional police powers.

They may enact and enforce laws concerning subjects such as:

• criminal conduct;
• public safety;
• licensing;
• education;
• employment in areas not preempted by federal law;
• property;
• family relationships; and
• administration of state government.

But state law cannot simply replace federal immigration law.

The Supreme Court’s decision in Arizona v. United States is a central authority concerning federal preemption in immigration law. The Court held that several provisions of Arizona’s immigration-enforcement statute were preempted because immigration regulation is an area in which federal authority is particularly strong and the challenged provisions conflicted with the federal system.

This does not mean that every state law affecting noncitizens is unconstitutional.

Rather, courts must examine the particular state law, its purpose and operation, the federal statutory framework, and the applicable constitutional doctrines.

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The Supremacy Clause and Immigration Law

The Supremacy Clause is central to the relationship between federal and state immigration law.

Under Article VI of the Constitution, valid federal law takes precedence over conflicting state law.

Immigration provides an especially important example of this principle because Congress has established a comprehensive federal regulatory system.

A state cannot simply declare that federal immigration law does not apply within its borders.

At the same time, federal supremacy does not mean that the federal government can command state governments to perform every federal function. Constitutional federalism imposes limits on federal commandeering of state governments.

The sanctuary and anti-sanctuary debates discussed elsewhere in immigration law are therefore examples of a broader constitutional question:

Where does federal immigration authority end, and where does state governmental authority begin?

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Immigration Law and Individual Rights

Federal immigration power is broad, but it is not unlimited.

People who are physically present in the United States can have constitutional protections even when they are not citizens.

Depending on the circumstances, immigration cases may involve:

• due process;
• equal protection;
• freedom of speech;
• protection against unreasonable searches and seizures;
• access to courts;
• procedural protections in immigration proceedings; and
• other constitutional rights.

The scope of those protections can vary depending on the person’s status, location, and the type of governmental action involved.

The distinction between a person seeking initial admission and a person already within the United States has historically been important in Supreme Court immigration jurisprudence. The constitutional framework governing admission at the border can differ from the protections applicable to persons who have already established a presence within the country.

This is one reason immigration law cannot be reduced to the statement that “noncitizens have no rights.”

The legal reality is considerably more nuanced.

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The Federal Government’s Plenary Power Over Immigration

American immigration law has traditionally been associated with the plenary power doctrine.

Under this doctrine, the political branches—particularly Congress and the executive branch acting pursuant to congressional authority—have historically received substantial judicial deference in matters involving the admission and exclusion of foreign nationals.

The Supreme Court has described congressional authority over immigration as exceptionally broad.

The U.S. Constitution Annotated explains that this power is strongest in matters involving foreign nationals who have not yet entered the United States, while constitutional limitations become particularly important when the government acts against people already physically present in the country.

The plenary-power doctrine does not mean that immigration decisions are completely beyond judicial review.

Courts continue to interpret statutes, review agency action within their jurisdiction, enforce constitutional requirements, and resolve questions concerning the legality of executive and administrative action.

The doctrine instead reflects the historically strong role assigned to the political branches in determining national immigration policy.

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Immigration Law and Naturalization

Immigration law also governs the legal transition from noncitizen to citizen through naturalization.

The Constitution gives Congress the authority to establish a uniform rule of naturalization.

Congress exercised this authority through federal naturalization statutes, now principally contained within the INA.

Cornell’s Legal Information Institute explains that Congress possesses the constitutional naturalization power and that the INA establishes the governing framework for naturalization.

Naturalization is therefore part of the broader immigration-law system, although citizenship law extends beyond immigration in the ordinary sense.

A person who becomes a naturalized citizen generally acquires U.S. citizenship with the rights and responsibilities associated with citizenship, subject to the constitutional and statutory framework governing citizenship.

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Immigration Law Is More Than Visa Law

One of the most common misconceptions about immigration law is that it is essentially a system for obtaining visas.

Visas are important, but they represent only one part of the legal system.

Immigration law also addresses:

• citizenship;
• nationality;
• permanent residence;
• temporary immigration status;
• asylum;
• refugee protection;
• employment;
• family-based immigration;
• humanitarian programs;
• immigration detention;
• removal proceedings;
• immigration-related criminal offenses;
• administrative appeals;
• judicial review;
• state and federal immigration conflicts; and
• naturalization.

A person may therefore encounter immigration law without ever applying for a visa.

For example, an individual born abroad may acquire U.S. citizenship through a parent, seek asylum after entering the country, obtain lawful permanent residence through adjustment of status, face removal proceedings, or apply for naturalization years after becoming a permanent resident.

Each situation involves a different part of the same broader legal system.

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Why Immigration Law Is So Complex

U.S. immigration law is complex because several different legal systems operate simultaneously.

First, there is federal statutory law, particularly the INA.

Second, there are federal regulations implementing congressional statutes.

Third, there is a substantial body of judicial precedent interpreting those laws.

Fourth, there are administrative agencies applying the law to individual cases.

Fifth, immigration law interacts with other areas of federal law, including criminal law, administrative law, constitutional law, employment law, family law, and international affairs.

Finally, immigration law is continually affected by congressional amendments, executive action, agency policy, litigation, and judicial decisions.

The result is a legal field in which a seemingly simple question—such as “Can this person enter the United States?”—may require analysis of citizenship, visa classification, admissibility, prior immigration history, statutory exceptions, agency procedures, and constitutional principles.

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A Framework for Studying U.S. Immigration Law

A useful way to approach U.S. immigration law is to divide it into several major areas.

Citizenship and Nationality

This area asks who is a U.S. citizen or national and how citizenship may be acquired, derived, or naturalized.

Visas and Admission

This area concerns immigrant and nonimmigrant visas, inspection, admission, and the legal grounds on which a person may be denied admission.

Lawful Permanent Residence

This area concerns the legal status commonly known as a green card and the various statutory routes to permanent residence.

Nonimmigrant Status

This includes temporary classifications for visitors, students, workers, diplomats, and other categories.

Humanitarian Protection

This includes asylum, refugee protection, temporary protected status, and other humanitarian mechanisms established by federal law.

Immigration Enforcement

This includes investigations, detention, removal proceedings, expedited removal, and other federal enforcement mechanisms.

Immigration Consequences of Criminal Conduct

This area examines when criminal convictions or conduct affect admissibility, removability, or other immigration benefits.

Family-Based Immigration

This concerns immigration classifications based on qualifying family relationships.

Employment-Based Immigration

This concerns temporary employment classifications and immigrant employment categories.

Naturalization

This concerns the process through which eligible noncitizens may become U.S. citizens.

Federalism and State Immigration Laws

This area examines the relationship between federal immigration authority and state or local governmental power, including preemption and sanctuary-law disputes.

These categories overlap, but together they provide a useful map of the field.

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What Makes U.S. Immigration Law Different From Ordinary State Law?

Many areas of American law are primarily state-based.

Criminal law, family law, property law, contract law, and tort law are often governed substantially by state statutes and state judicial decisions.

Immigration law is different.

The central rules concerning admission, immigration status, removal, and naturalization are established through federal law.

This national structure exists because immigration implicates national borders, foreign relations, citizenship, and the United States’ relationship with other nations.

Allowing every state to establish an independent system governing who may enter or remain in the country would undermine the national character of those functions.

That is why federal immigration authority has traditionally been treated as particularly strong.

At the same time, state laws can still affect noncitizens in areas that fall within legitimate state authority.

The legal question is therefore not whether states can ever regulate conduct involving immigrants. They plainly can.

The question is whether the state is regulating an area within its lawful authority or attempting to regulate immigration in a manner displaced by federal law.

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Key Takeaways

U.S. immigration law is a broad body of federal law governing the legal relationship between the United States and people who are not U.S. citizens or nationals.

The most important foundations are:

1. Immigration law is primarily federal law.
2. Congress is the principal lawmaking authority in immigration and naturalization.
3. The Immigration and Nationality Act is the central federal immigration statute.
4. The Constitution provides both sources of federal authority and limits on governmental power.
5. Federal regulations implement many provisions of the INA.
6. Federal courts interpret immigration statutes and constitutional provisions.
7. Multiple federal agencies administer different parts of the immigration system.
8. A visa is not the same thing as admission to the United States.
9. Immigration status is not the same thing as citizenship.
10. Inadmissibility and removability are different legal concepts.
11. States retain authority over many matters involving noncitizens but cannot override valid federal immigration law.
12. The Supremacy Clause and federal preemption are central to conflicts between federal and state immigration laws.
13. The federal government’s immigration power is historically broad, particularly concerning admission and exclusion.
14. Noncitizens physically present in the United States can possess constitutional rights and protections.
15. Naturalization is a federal process governed principally by congressional law.

The most useful way to understand U.S. immigration law is therefore not as a collection of visa applications and immigration forms, but as a comprehensive federal legal system governing entry, admission, status, residence, protection, enforcement, removal, and citizenship.

Once this framework is understood, the more specialized areas of immigration law become much easier to place in context.

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Frequently Asked Questions

What is U.S. immigration law?

U.S. immigration law is the body of federal statutes, regulations, judicial decisions, and administrative rules governing immigration into and within the United States, including admission, visas, immigration status, permanent residence, humanitarian protection, removal, and naturalization.

Is immigration law federal or state law?

Immigration law is primarily federal. Congress establishes the principal statutory framework, and federal agencies administer it. States nevertheless retain authority over many matters involving noncitizens, provided their laws do not conflict with federal law or violate the Constitution.

What is the main U.S. immigration law?

The Immigration and Nationality Act (INA) is the principal federal immigration statute. It is codified primarily in Title 8 of the United States Code.

Who makes U.S. immigration law?

Congress makes federal immigration statutes. Executive agencies administer and enforce those statutes through regulations and other authorized actions, while federal courts interpret the Constitution and federal immigration laws.

What is the difference between a visa and immigration status?

A visa generally allows a person to seek entry to the United States at a port of entry. Immigration status concerns the legal classification under which a person is present in the United States. A visa and a person’s status are therefore related but distinct legal concepts.

What is the difference between an immigrant and a nonimmigrant?

An immigrant generally enters the United States for permanent residence, while a nonimmigrant is admitted for a temporary purpose under a specific statutory classification.

What is inadmissibility?

Inadmissibility refers to statutory grounds that can prevent a person from being admitted to the United States. Many grounds of inadmissibility are contained in INA §212, codified at 8 U.S.C. §1182.

What is removability?

Removability refers to the statutory grounds under which a noncitizen who is subject to U.S. immigration jurisdiction may be removed from the United States. Many grounds are contained in INA §237, codified at 8 U.S.C. §1227.

Can states make their own immigration laws?

States can enact laws concerning matters within their constitutional authority, including many ordinary criminal and public-safety matters. However, state laws that conflict with or are preempted by federal immigration law may be invalid.

Do noncitizens have constitutional rights?

Yes. Noncitizens in the United States can possess constitutional rights and protections. The precise scope of those protections can depend on the person’s location, immigration status, and the governmental action involved.

Is naturalization part of immigration law?

Yes. Naturalization is a major component of federal nationality and immigration law. Congress has constitutional authority to establish a uniform rule of naturalization, and the INA provides the principal statutory framework.

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This article provides general information about U.S. immigration law and is intended for educational purposes. Immigration statutes, regulations, agency policies, and judicial interpretations can change, and the application of immigration law depends on the particular facts and legal circumstances of each case.