U.S. Immigration and Customs Enforcement:
Mission, Structure, Authorities, and Legal Limits
Date of Information: 08/19/2025
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Overview
U.S. Immigration and Customs Enforcement (ICE) is the Department of Homeland Security’s principal interior enforcement and investigative agency. While CBP serves as the first line of defense at and near the border, ICE focuses on interior immigration enforcement, detention and removal operations, and complex criminal investigations with transnational dimensions.
Immigration and Customs Enforcement: Distinct Missions Under One Umbrella
ICE is often portrayed in public debate as a single, monolithic enforcement body. In reality, ICE is composed of three separate subcomponents (two directorates and one office), each with a distinct mission and operational focus. Understanding these distinctions is critical for separating rhetoric from reality.
Core Components: Three Sub-Agencies, Three Missions
Enforcement and Removal Operations (ERO):
Handles arrests, detention, custody determinations, and removals under the Immigration and Nationality Act (INA). This is the operational arm that conducts at-large arrests, jail transfers, and removal flights. Most of the public controversy surrounding ICE is directed at ERO.Homeland Security Investigations (HSI):
ICE’s federal criminal investigative division. HSI investigates human smuggling and trafficking, worksite crime, visa and benefit fraud, sanctions evasion, export control violations, money laundering, IP theft, cybercrime, and child exploitation. Its mission intersects with FBI, DOJ, and international partners, but is distinct from ERO’s focus on civil removals.Office of the Principal Legal Advisor (OPLA):
The largest legal office within DHS. OPLA attorneys represent the government in immigration court, prosecute removal cases, issue legal opinions, and advise ERO on enforcement. OPLA is the litigating arm of ICE before EOIR.
⚠️Why This Distinction Matters
There is currently a heated political and social debate about ICE’s role, with many calling for its abolition or defunding. However, the rancor is disproportionately directed at Enforcement and Removal Operations. Both Homeland Security Investigations and the Office of the Principal Legal Advisor have critical but different missions that intersect with ERO without being synonymous with it.
In short, ICE is not one single mission — it is three distinct organizations housed under the same umbrella, each operating with a different focus. Understanding that separation is essential for making informed judgments about ICE’s place within the Department of Homeland Security and the broader national security framework.
Jurisdiction & Typical Operating Environment
Geographic scope: Nationwide, with emphasis on interior operations (workplaces, residences, detention centers, jails/prisons, transportation hubs).
Worksite/document enforcement: HSI leads criminal cases; ERO carries out civil arrests flowing from audits and raids.
Jail/custody transfers: ERO frequently issues immigration detainers requesting transfer or notification from state/local facilities.
Legal Authorities (High Level)
Jurisdictional Note: Unlike U.S. Customs and Border Protection, whose powers are territorially tethered to the border and its functional equivalents, ICE’s sub-agencies are not limited by geography in the same way. Each has a defined subject-matter mission, but ICE personnel may operate anywhere in the United States so long as their activity falls within the laws they are tasked to enforce. While ICE is not the FBI — it does not have plenary authority over all federal crimes — its Enforcement and Removal Operations, Homeland Security Investigations, and OPLA attorneys may all conduct operations nationwide. Those operations remain subject to the Fourth, Fifth, and Sixth Amendments: constitutional standards governing searches, seizures, interrogations, and prosecutions apply to ICE agents and attorneys just as they do to other federal law enforcement officials.
Civil immigration (ERO & OPLA):
Immigration and Nationality Act provisions (8 U.S.C. § 1357 et seq.).
Administrative warrants (Forms I-200, I-205).
Custody statutes: 8 U.S.C. § 1226 (pre-removal) and § 1231 (post-removal).
Criminal investigative (HSI):
Titles 18, 19, 21, and 50 (general crimes, customs, narcotics, national security).
Grand jury subpoenas, search warrants, MLAT requests.
What Each Bureau Within ICE Can Do
Enforcement and Removal Operations (ERO):
Arrest and detain noncitizens for civil immigration violations.
Issue immigration detainers to request transfer or notification from state and local jails.
Manage detention facilities, custody decisions, and removal (deportation) operations.
Facilities: ICE contracts with public and private facilities nationwide.
Alternatives to detention (ATD): Case management, check-ins, electronic monitoring.
Bond/parole: Certain detainees may qualify for release on bond or parole depending on statutory eligibility.
Homeland Security Investigations (HSI):
Conduct federal criminal investigations into smuggling, trafficking, fraud, money laundering, and sanctions/export control violations.
Use grand jury subpoenas, search warrants, and international cooperation tools (e.g., MLATs) to pursue transnational crime.
Partner with DOJ, FBI, and international law enforcement to dismantle organized criminal networks.
Office of the Principal Legal Advisor (OPLA):
Prosecute immigration cases before the Executive Office for Immigration Review (EOIR).
Provide legal advice to ICE officers on enforcement, detention, and removal matters.
Key Limits & Constitutional Guardrails
No general police power: Like all federal law enforcement agencies, ICE cannot enforce unrelated state law absent explicit authority.
Fourth Amendment:
Homes: Entry requires consent or judicial warrant. Administrative warrants do not authorize non-consensual entry.
Stops/arrests in public: Must meet reasonable suspicion/probable cause thresholds.
Detainers: Requests only — cannot compel local agencies to hold someone without their own authority. See Printz v. United States, 521 U.S. 898 (1997). Federal courts have applied this principle directly to immigration detainers. See Galarza v. Szalczyk, 745 F.3d 634 (3d Cir. 2014) (detainers are voluntary requests, not commands, and local agencies may be liable if they detain individuals without independent legal authority); Morales v. Chadbourne, 793 F.3d 208 (1st Cir. 2015) — holding a U.S. citizen on an ICE detainer without probable cause violated the Fourth Amendment.
Sensitive locations policy: Enforcement actions are limited in places like schools, hospitals, and churches (subject to exigency).
Due process: Noncitizens have rights to notice, hearings, and counsel at no expense to the government.
Public Rhetoric: “Abolish ICE”
In recent years, ICE has become a flashpoint in national debate. Calls to abolish or defund ICE are almost entirely directed at Enforcement and Removal Operations due to its high-visibility role in arrests, detention, and removals.
ERO is the target of most public rancor.
HSI and OPLA have distinct missions that intersect with, but are not identical to, ERO.
Understanding ICE as three subcomponents with different mandates is critical to making informed judgments about its role within DHS.
CBP vs. ICE — At a Glance
Practical Guidance: Rights in ICE Encounters
At home: You do not need to open the door unless shown a judicial warrant signed by a judge (with correct name/address).
On the street/workplace: Ask if you are free to leave. Request a lawyer. Provide ID truthfully but avoid false statements.
In custody: Ask for a lawyer and copies of any detainer, warrant, or Notice to Appear. Record or note the nine-digit A-Number.
Check-ins with ERO: For advice on how to handle required check-ins with ICE Enforcement and Removal Operations (ERO) while you are in removal proceedings, please see our Guide on ICE Check-Ins During Deportation Proceedings.
Practical Guidance: Rights in ICE Encounters
At home: You do not need to open the door unless shown a judicial warrant signed by a judge (with correct name/address).
On the street/workplace: Ask if you are free to leave. Request a lawyer. Provide ID truthfully but avoid false statements.
In custody: Ask for a lawyer and copies of any detainer, warrant, or Notice to Appear. Record or note the nine-digit A-Number.
Check-ins with ERO: For advice on how to handle required check-ins with ICE Enforcement and Removal Operations (ERO) while you are in removal proceedings, please see our Guide on ICE Check-Ins During Deportation Proceedings.
Frequently Asked Questions About ICE (Immigration & Customs Enforcement)
1) What is ICE and what does it do?
ICE is a Department of Homeland Security (DHS) agency that enforces civil immigration laws and certain criminal statutes. Its main divisions are Enforcement and Removal Operations (ERO) and Homeland Security Investigations (HSI).
2) What’s the difference between ERO and HSI?
ERO handles arrests, detention, supervision, and removals in civil immigration cases. HSI investigates criminal activity (e.g., trafficking, fraud). Many people interact with ERO for check-ins, detention, and removal logistics.
3) Is OPLA part of ICE?
Yes. The Office of the Principal Legal Advisor (OPLA) is ICE’s legal office. OPLA attorneys are the prosecutors in Immigration Court (EOIR). (Your court hearings are run by DOJ/EOIR, not ICE.)
4) What is an ICE detainer?
A detainer asks a local jail/police agency to notify ICE before release and to hold someone briefly for transfer to ICE custody. Detainers are not criminal warrants; state/local response policies vary.
5) What happens after ICE arrests someone?
ERO may detain the person, set a release (on recognizance, parole, or bond), or place them on Alternatives to Detention (ATD) programs (e.g., ISAP with smartphone app, ankle monitor, or phone reporting).
6) Bond vs. parole—what’s the difference?
Bond is a monetary guarantee (set by ICE or an Immigration Judge) to ensure appearances. Parole is discretionary release based on humanitarian need or public benefit and usually doesn’t require payment.
7) Can I ask ICE to lower bond or release me?
Yes. You or your attorney can request custody review or file for bond redetermination before an Immigration Judge (where eligible). Provide documents showing community ties, address, sponsor, and low flight risk.
8) What is ATD/ISAP?
Alternatives to Detention are supervision tools (app check-ins, voice ID, in-person reporting, or GPS). Compliance matters—violations can trigger stricter conditions or detention.
9) What is an ICE check-in and what should I bring?
A check-in is a required meeting (often at a local ERO office). Bring ID, address proof, any court notices, and attorney info. Ask for a next report date in writing and keep all receipts/notices.
10) Does ICE control the Immigration Court case?
No. EOIR (DOJ) controls court schedules and decisions. ICE/OPLA prosecutes the case; ERO handles custody and removals. Court motions/appeals go to EOIR/BIA; ICE manages detention and travel.
11) Can ICE remove me while I’m appealing?
If you have a final removal order and no stay of removal in place, removal can proceed. Your lawyer can seek a BIA/circuit-court stay and/or file Form I-246 (Stay of Removal) with ICE to pause removal temporarily (discretionary).
12) What is Form I-246 (Stay of Removal)?
It’s a request to ICE ERO asking them to pause removal for humanitarian or case-related reasons. Include evidence (medical, family hardship, pending relief). Decisions are discretionary and time-sensitive.
13) How does “prosecutorial discretion” (PD) work with ICE?
PD can include release, lower bond, reporting changes, or, via OPLA, dismissal or narrowing the court case. Strong equities (family, health, victim status, military service) and clear eligibility for relief help.
14) If I win relief in court, does ICE still supervise me?
Once relief is granted and final, ERO should update records and end removal supervision. Keep copies of the order and follow up if supervision isn’t lifted promptly.
15) How do I file complaints about treatment or conditions?
You can submit complaints to ICE ERO, HSI, DHS CRCL (Civil Rights & Civil Liberties), or the DHS OIG. Document dates, locations, names, and witnesses.
16) How do I get my ICE/immigration records?
Request records via FOIA to the relevant DHS components (ICE, CBP, USCIS). Ask your attorney which agency is likeliest to hold the documents you need (A-file, I-213, booking records, travel history).
17) What if I move while on ICE supervision?
You must promptly update address with EOIR (for court) and with ICE ERO (for supervision). Missing updates can cause missed notices and violations.
18) Do I need a lawyer to deal with ICE?
Not required—but having counsel helps with PD requests, bond hearings, I-246 stays, FOIA, and coordination between ERO, OPLA, and the court.
When to Call Us
If you or a loved one is in ICE custody, has received a Notice to Appear, is facing a worksite audit, or is under HSI investigation, we can help. Schedule a consultation today to speak with an experienced immigration and national security attorney.
Other Helpful Resources:
See Also:
CIL Guide to the Circumvention of Lawful Pathways Rule
CIL Guide to the U.S. Customs and Border Protection Agency
