Understanding Federal Law Enforcement in the United States Part 3—U.S. Immigration and Customs Enforcement

This is the third in a six-part series examining major policing strategies through a research-grounded lens, assessing each strategy against multiple criteria.

When federal agents in plain clothes and tactical gear appeared at car washes, worksites, and bus stops across American cities in recent months, many residents had the same question: Who are these people, and what authority do they have to be here? In most cases, the answer was U.S. Immigration and Customs Enforcement (ICE)—an agency that most Americans have heard of but few could describe with precision.

ICE is the federal agency responsible for immigration enforcement in the interior of the United States and for criminal investigations involving cross-border violations. With more than 20,000 law enforcement and support personnel—a figure that grew significantly following a 2025 hiring surge—operating out of more than 400 offices domestically and in approximately 50 countries, ICE enforces more than 400 federal statutes. It shares a parent department and legislative origin with U.S. Customs and Border Protection (CBP); however, where CBP’s jurisdiction is anchored at and near the border, ICE’s operational footprint is centered in the nation’s interior.

Creation and Legislative Origins

Prior to Sept. 11, 2001, the functions ICE now performs were divided between two agencies housed in two different departments:

• The Immigration and Naturalization Service (INS) was responsible for immigration services and interior enforcement as part of the Department of Justice (DOJ).
• The U.S. Customs Service oversaw customs investigations and trade enforcement as part of the Treasury Department.

The Homeland Security Act of 2002 restructured that arrangement. As examined in Part 2 of this series, the Sept. 11 attacks revealed significant coordination failures among the agencies responsible for customs, immigration, and national security—entities that operated across separate departments without a common intelligence framework or counter-terrorism mission. Congress responded by consolidating 22 federal agencies under the newly created Department of Homeland Security (DHS).

On March 1, 2003, the investigative and interior enforcement components of the former Customs Service and INS combined to form a single new agency: the Bureau of Immigration and Customs Enforcement, subsequently renamed U.S. Immigration and Customs Enforcement. Congress equipped ICE with a combination of civil and criminal authorities specifically designed to address the vulnerabilities that allowed coordination failures to persist.

Although the simultaneous creation of ICE and CBP from the same legislative act means the two agencies share a common origin, Congress designed them to fill different roles. CBP assumed responsibility for border security—screening people and goods at ports of entry and patrolling the territory between them—while ICE took on interior enforcement and criminal investigations involving cross-border activity. That structural division has shaped each agency’s mission ever since, even where day-to-day operations have complicated the boundary between them.

Mission

ICE’s stated mission is to “protect America through criminal investigations and enforcing immigration laws to preserve national security and public safety.” The agency carries out this mission via two primary operational divisions with distinct mandates.

Enforcement and Removal Operations (ERO) is responsible for identifying, arresting, detaining, and removing individuals who are in the United States unlawfully. Immigration enforcement constitutes the single largest area of responsibility for ERO. While ERO maintains assets near the border, ICE states that the majority of its immigration enforcement mission takes place in the interior of the country—a distinction that separates ERO’s work from CBP’s border-focused operations.

Homeland Security Investigations (HSI) is ICE’s principal investigative component and the largest investigative arm of the DHS. HSI’s mandate extends well beyond immigration, with special agents investigating transnational criminal organizations and terrorist networks that exploit customs and immigration systems. HSI has broad legal authority to pursue federal criminal cases involving narcotics smuggling, human trafficking, weapons trafficking, money laundering, child exploitation, cybercrime, intellectual property theft, trade fraud, and export control violations. Its special agents, criminal analysts, and mission support personnel operate from 235 domestic offices and over 90 offices in more than 50 countries, making it one of the largest international law enforcement presences maintained by any federal agency. ICE’s offices of Investigations, Intelligence, and International Affairs combined to create HSI in June 2010.

How aggressively ICE pursues its interior enforcement mission has varied. Prior administrations have issued guidance directing officers to prioritize individuals posing threats to national security or public safety, while others have directed broader enforcement extending to anyone present in violation of immigration law. The distance between ICE’s stated mission and its deployment in any given period reflects policy choices that successive administrations have made differently.

ICE’s operational role continues to evolve in real time. In March 2026, a partial shutdown of DHS funding left Transportation Security Administration officers working without pay, leading to rising callout rates and long security lines at airports across the country. President Trump directed the deployment of hundreds of ICE officers to several major airports to assist with crowd management, line control, and other non-screening functions. The deployment placed an agency created to enforce immigration and customs law into an airport-security support role—an assignment far afield from the mission Congress established in 2003.

Scale

Prior to 2025, ICE employed approximately 20,000 law enforcement and support personnel, with ERO maintaining roughly 6,000 deportation officers. Signed into law on July 4, 2025, the One Big Beautiful Bill Act dramatically changed the agency’s scale by providing approximately $75 billion over four years—roughly $30 billion for hiring, training, and enforcement operations and $45 billion for expanding detention capacity. The legislation funded the hiring of 10,000 new ERO officers. In early 2026, the DHS announced that ICE had more than doubled its officers and agents from roughly 10,000 to more than 22,000. The agency’s combined budget (base appropriations plus supplemental funding) placed it among the highest-funded federal law enforcement agencies in the country.

Jurisdiction

ICE derives its enforcement authority primarily from Title 8 of the U.S. Code (federal immigration and nationality law), while HSI also enforces statutes under Titles 18 (federal criminal law), 19 (customs law), and 21 (Controlled Substances Act).

Under Section 287(a)(2) of the Immigration and Nationality Act and its implementing regulations, ICE officers may make warrantless arrests (i.e., arrests without prior court approval) when they have “reason to believe” a person’s presence in the United States violates immigration law and that they are “likely to escape before a warrant can be obtained.” Courts have interpreted the “reason to believe” standard as equivalent to probable cause under the Fourth Amendment—the constitutional provision that protects against unreasonable searches and seizures.

A key but often misunderstood distinction in ICE enforcement involves the difference between administrative and judicial warrants. ICE routinely uses administrative warrants (internal agency documents signed by ICE officials, not judges) to authorize the arrest of individuals for immigration violations. These warrants are “purely administrative” and “do not confer the same authority as judicially approved arrest warrants.” The Supreme Court has long held that the Fourth Amendment generally prohibits nonconsensual entry into a home without a judicial warrant (issued and signed by a judge). Meanwhile, lower courts have found ICE agents in violation of the Fourth Amendment for forcibly entering homes with administrative warrants only and without recognized exception, such as exigent circumstances (i.e., emergency situations like an immediate threat to safety) or consent.

In May 2025, ICE’s Acting Director, Todd Lyons, signed an internal memo stating that Form I-205 administrative warrants alone could authorize forced entry into the residences of individuals with final orders of removal—a departure from the agency’s practice across prior administrations. Disclosed publicly in January 2026, the memo acknowledged that the DHS “has not historically relied on administrative warrants alone” for this purpose. A federal district court in Minnesota subsequently ruled that at least one such entry violated the Fourth Amendment. In March 2026, the DOJ separately acknowledged in a federal court filing that it had erroneously relied on an ICE memo to justify arrests at immigration courthouses for nearly a year and that the memo had never applied to civil enforcement actions in or near immigration courts, which fall under DOJ jurisdiction rather than DHS.

Courts have also scrutinized the legal standard that governs when ICE agents may initiate a stop in the first place. The question of what constitutes “reasonable suspicion”—the legal standard requiring officers to point to specific facts justifying a brief investigative stop—for immigration stops in the interior became the subject of major litigation in 2025. When ICE launched enforcement operations in the Los Angeles area in June, residents filed suit alleging that agents were conducting stops based on factors like apparent ethnicity, language spoken, type of employment, and presence at certain locations without individualized suspicion tied to a specific person. A federal district judge in the Central District of California issued a temporary restraining order restricting such stops, and the Ninth Circuit Court of Appeals upheld that order.

On Sept. 8, 2025, the Supreme Court stayed the district court’s order in Noem v. Vasquez Perdomo, allowing enforcement operations to resume while the case continued. The Court’s brief, unsigned order offered no reasoning for this. In a solo concurrence, Justice Brett Kavanaugh wrote that factors like the demographic characteristics of an area, the language an individual speaks, and the type of location where a stop occurs could be relevant to a reasonable suspicion analysis under the totality of the circumstances—meaning a court should weigh all relevant factors together rather than evaluating each in isolation. The three dissenting justices argued that the Court’s order permitted stops that the 1975 precedent in United States v. Brignoni-Ponce was designed to prevent. The case remains in active litigation.

One of ICE’s primary mechanisms for extending its enforcement reach beyond its own personnel is the 287(g) program, authorized under Section 287(g) of the Immigration and Nationality Act. This program allows ICE to enter into formal partnership agreements with state and local law enforcement agencies, delegating limited immigration enforcement functions to local officers operating under ICE’s direction and oversight. As of March 2026, ICE has signed 1,552 memoranda of agreement covering 39 states and two U.S. territories—a substantial expansion from the 141 agreements in 25 states that existed as recently as fiscal year 2019.

Another significant policy change affecting ICE’s operational footprint involves enforcement locations. Since 2011, the DHS had maintained a “sensitive locations” policy restricting ICE and CBP enforcement actions at schools, hospitals, places of worship, and similar locations absent exigent circumstances. In 2021, the Biden administration expanded and renamed this framework as a “protected areas” policy. That policy was rescinded on Jan. 20, 2025, with officers directed to apply enforcement discretion with “a healthy dose of common sense.” A federal court has since issued a preliminary injunction requiring the DHS to maintain some restrictions at plaintiffs’ places of worship under the First Amendment and the Religious Freedom Restoration Act, but the broader framework no longer applies as DHS policy.

Hiring and Training

ICE maintains separate hiring and training pipelines for its two law enforcement components, ERO and HSI. All applicants for law enforcement positions must be U.S. citizens and must pass a background investigation, medical evaluation, drug test, and physical fitness assessment.

ERO deportation officers attend training at the ICE Academy at the Federal Law Enforcement Training Centers (FLETC) in Glynco, Georgia. The Basic Immigration Enforcement Training Program initially ran for 16 weeks, with an additional 25-day Spanish language course for officers who did not demonstrate proficiency. But in 2025, the DHS restructured ERO training to a 42-day program as part of a hiring surge to onboard thousands of new personnel. The agency stated that the revised curriculum eliminated redundancy and incorporated technology advancements while maintaining the same subject matter standards; however, the mandatory Spanish language course was replaced with translation and interpretation services for officers in the field. The DHS Inspector General has opened an investigation into ICE’s hiring and training practices that will assess the agency’s ability to meet operational needs under the accelerated timeline.

HSI agents follow a longer training pipeline. Candidates first complete the Criminal Investigator Training Program—a 12-week foundational course shared with other federal investigative agencies—followed by HSI Special Agent Training, a 15-week program covering customs and immigration law, financial investigations, cybercrime, narcotics trafficking, child exploitation, and tactical techniques. According to the DHS, HSI candidates receive more than 100 days of specialized training in total.

Training across both components covers arrest techniques, defensive tactics, firearms and marksmanship, immigration and constitutional law, conflict management, de-escalation techniques, and emergency vehicle operations. The DHS states that training includes multiple classes dedicated to use-of-force policy and the proper application of force. ICE’s use-of-force directive requires officers to use force only when no reasonably effective, safe, and feasible alternative exists, and only at the level that is objectively reasonable under the totality of the circumstances—a standard derived from the Supreme Court’s framework in Graham v. Connor. Officers are also required to employ de-escalation tactics when practical. Following academy graduation, all ICE officers must undergo supervised on-the-job training and mentorship, which the DHS states is tracked and monitored.

Looking Ahead

The next installment examines the Federal Bureau of Investigation (FBI), the oldest and largest of the three DOJ agencies covered in this series. Where ICE’s authority is rooted in immigration and customs law and its operational footprint has expanded into new arenas in recent months, the FBI draws on the broadest statutory mandate of any federal law enforcement agency. While the two agencies occasionally collaborate on investigations involving transnational crime, their missions, organizational cultures, and the public debates surrounding them differ substantially.

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Next in this series: Part 4—Federal Bureau of Investigation