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 100 air miles from any land border or coastline (8 CFR 287.1(a)(2)). 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 does not consent to warrantless sweeps of its buses (following a Washington State investigation); 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:

• US citizens cannot be denied entry for declining to unlock a device — but the device can be detained.
• LPRs generally cannot be denied entry for refusal alone, though devices can be held and the encounter documented.
• Visa holders and other non-residents can be refused admission for declining inspection.
• 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.

Where expedited removal fits

While the January 2025 nationwide expansion remains stayed, the operative expedited-removal designations are border-tied: arrival at ports of entry, or apprehension within 100 miles of a land border within 14 days of entry. The zone is where that summary process actually operates today — the full explainer 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: 2026-06-11. 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.