The 100-mile border zone — checkpoints, bus and train checks, and device searches at ports of entry

The 100-mile border zone — what changes near the border, and what never does

Federal law gives immigration officers extra authority within a “reasonable distance” of any external boundary of the United States — defined by regulation as up to 100 air miles from the land borders or the territorial sea, which extends 12 nautical miles from the coastal baselines (8 CFR 287.1(a)). The same rule lets the CBP Commissioner or ICE’s Assistant Secretary approve a longer distance when a chief patrol agent or special agent in charge reports that unusual circumstances make it reasonable (8 CFR 287.1(b)). That zone covers entire states (Florida, Michigan, Maine, Hawaii) and most of the largest US cities. Knowing which rules change inside the zone — and which constitutional protections never change — matters for anyone who commutes, rides interstate buses, or flies. General information, not legal advice.

What the zone is — and is not

Within 100 air miles of a border or coast, INA §287(a)(3) authorizes immigration officers, without a warrant, to board and search vehicles, trains, buses, boats, and aircraft in search of noncitizens. The American Civil Liberties Union estimates that roughly two in three US residents live inside the zone.

What the zone does not do:

• It does not suspend the Constitution. The 4th and 5th Amendments apply with full force.
• It does not allow warrantless entry into homes. The within-25-miles private-property access in §287(a)(3) expressly excludes dwellings.
• It does not create a general stop-and-search power on the street. Outside ports of entry, stops still require the ordinary legal standards described below.

Fixed checkpoints

Permanent and tactical Border Patrol checkpoints (common on highways in the Southwest, but lawful anywhere in the zone) operate under United States v. Martinez-Fuerte, 428 U.S. 543 (1976):

• Agents may briefly stop every vehicle and ask about citizenship/immigration status — no individualized suspicion needed.
• Agents may refer a vehicle to “secondary inspection” for brief further questioning.
• Agents may not search the vehicle’s interior without probable cause or consent.
• You retain the right to remain silent (“I am exercising my right to remain silent”) and the right to refuse consent (“I do not consent to a search”) — stated calmly. Refusing to answer may extend the stop; lying or false documents are federal offenses (18 U.S.C. §1001, §1546).

Roving patrols

Away from checkpoints, agents in vehicles may stop a car only with reasonable suspicion that it contains people unlawfully present (United States v. Brignoni-Ponce, 422 U.S. 873 (1975)) — and may not search it without probable cause (Almeida-Sanchez v. United States, 413 U.S. 266 (1973), striking down a warrantless roving search 25 miles from the border). Apparent ethnicity alone does not justify a stop.

Buses, trains, and transportation checks

Officers board interstate buses and trains inside the zone and ask passengers about status. The legal texture:

• Questioning is consensual unless reasonable suspicion develops — passengers may remain silent and may decline searches of their belongings.
• You may ask: “Am I free to leave?” If yes, you may end the encounter.
• Carriers differ: Greyhound stated in 2020 that it would no longer allow warrantless sweeps of its buses (a week after a Border Patrol memo on bus sweeps was reported in the media), and a 2021 Washington State consent decree requires it to deny CBP agents permission to board its Washington buses without a warrant or reasonable suspicion; Amtrak police and CBP practices vary by route.
• The practical advice from rights organizations: stay calm, do not run, do not present false documents, and remember that anything said can be used in proceedings.

Ports of entry — a different legal world

At actual ports of entry (airports with international arrivals, land crossings, seaports), the border search exception applies — routine searches need no suspicion, and refusing inspection has direct consequences for admission. The sharpest modern issue is electronic devices:

• Scope of device searches: CBP’s device-search page (checked October 23, 2026) says the search includes only information resident on the device when it is presented for inspection. CBP says officers may not use the device to access information stored solely remotely.
• US citizens cannot be denied entry for declining to unlock a device — but the device can be detained.
• LPRs are not addressed separately on CBP’s device-search page; CBP says a device that cannot be inspected may be detained, and that its ability to inspect a device alone does not determine admissibility.
• Foreign nationals applying for admission (visa holders and other non-citizens) must establish that they are entitled to enter. If one refuses to present a device in a condition that allows inspection, CBP says it “may consider the foreign national’s noncompliance and the inability to inspect the device when making admissibility decisions” — though its ability to inspect a device “alone does not determine admissibility.”
• Devices in airplane mode with strong passcodes (not just biometrics) and minimal stored data reduce exposure — a widely published practice recommendation from digital-rights organizations.

Customs-Enforcement Areas at sea — new as of August 25, 2026, and NOT the same as the 100-mile zone

On August 25, 2026, the Commissioner of CBP declared four Customs-Enforcement Areas (CEAs) under section 1 of the Anti-Smuggling Act of 1935 (19 U.S.C. 1701), published as CBP Dec. No. 26-17 at 91 FR 54800. They took effect the same day.

Read the geography carefully, because it is the opposite of the 100-mile zone. The 100-mile zone reaches inland from the coast. A CEA sits on the high seas, adjacent to but OUTSIDE US customs waters — for most vessels, customs waters end four leagues (about 12 nautical miles) offshore, and each of these CEAs runs out to 24 nautical miles from the baseline. So a CEA covers water further out to sea, not more land. Nothing in this declaration changes what agents may do at an inland checkpoint, on a bus, or at your door.

The four areas, each out to 24 NM from baseline:

What the designation authorizes inside those waters. Customs officers and agents may “go on board of any vessel and examine the vessel and any merchandise or person on board, and bring the same into port,” and may pursue, seize or arrest vessels, merchandise or persons there in the same manner as anywhere in the United States (19 U.S.C. 1701(b); 19 U.S.C. 1581(a); 19 CFR 162.3). They may also enforce 18 U.S.C. 2237, which makes it a federal crime for a vessel’s master or operator to fail to heave to when ordered, to obstruct a boarding, or to give materially false information.

The stated purpose is interdicting “hovering vessels” used to smuggle cargo or people. CBP wrote each area to operate independently: if a court enjoins one CEA or part of a boundary, the declaration says the rest stay in force.

Where expedited removal fits

Since July 17, 2026 the January 2025 nationwide expansion has been in effect (D.C. Circuit order in Make the Road New York v. Mullin), so expedited removal is no longer limited to the border-tied designations: arrival at ports of entry, or apprehension within 100 miles of a land border within 14 days of entry. Those border-tied designations still apply inside the zone — the full explainer, including the interior expansion, is at expedited removal.

Related information

• Expedited removal — current scope and the credible-fear safeguard
• ICE in public — street encounters
• ICE traffic stops
• Right to remain silent
• Judicial vs administrative warrants
• CBP border crossings — live wait-time data

Last verified: 2026-09-24. General information, not legal advice. Checkpoint and port-of-entry practices vary by sector and change with policy — for a specific encounter or case, contact a licensed immigration attorney.