Searches and Seizures at the Border and the Fourth Amendment
Congressional research reportMar 30, 2021
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Searches and Seizures at the Border and the
Fourth Amendment
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R46601
SUMMARY
Searches and Seizures at the Border and the
Fourth Amendment
Congress has broad authority to regulate persons or items entering the United States, an authority
that is rooted in its power to regulate foreign commerce and to protect the integrity of the nation’s
borders. Exercising this authority, Congress has established a comprehensive framework that
authorizes federal law enforcement officers to inspect and search persons and property at the
border to ensure that their entry conforms with governing laws, including those relating to
customs and immigration.
R46601
March 30, 2021
Hillel R. Smith
Legislative Attorney
Kelsey Y. Santamaria
Legislative Attorney
While federal statutes confer substantial authority to conduct border searches, this authority is not
absolute. The Fourth Amendment to the U.S. Constitution forbids unreasonable government searches and seizures of “the
people,” and this limitation extends to searches conducted at the border. The touchstone of the Fourth Amendment is the
reasonableness of a search. The Supreme Court has recognized that searches at the border are “qualitatively different” from
those occurring in the interior of the United States, because persons entering the country have less robust expectations of
privacy, given the federal government’s broad power to safeguard the nation by examining persons seeking to enter its
territory. While law enforcement searches and seizures within the interior of the United States typically require a judicial
warrant supported by probable cause, federal officers may conduct routine inspections and searches of persons attempting to
cross the international border without a warrant or any particularized suspicion of unlawful activity. But a border search that
extends beyond a routine search and inspection may require at least reasonable suspicion. The Supreme Court has not
precisely defined the scope of a routine border search, but has suggested that highly intrusive searches may fall outside that
category and thus require heightened suspicion to withstand Fourth Amendment scrutiny. Thus, the Court has held that the
prolonged detention of an airplane traveler pending invasive medical tests required reasonable suspicion that the traveler was
a drug smuggler. Conversely, the Court has determined that the removal and disassembly of a fuel tank constituted a routine
border search where reasonable suspicion of unlawful activity was not required.
The Supreme Court and lower courts have applied this border search exception not only to the physical border itself, but also
to searches at the border’s “functional equivalent,” such as at a port of entry in the interior of the United States (e.g., an
international airport). Border-related searches and seizures in areas beyond the border or its functional equivalent are
generally subject to greater Fourth Amendment scrutiny. For example, government officers may conduct warrantless
“extended border searches” of individuals found within the United States if there is both reasonable certainty of a recent
border crossing and reasonable suspicion of unlawful activity. Government officers may also conduct certain warrantless
searches near the border that do not require evidence of a border crossing. For instance, “roving patrol” stops of vehicles near
the border to question the vehicle’s occupants are permissible if there is reasonable suspicion of unlawful activity, while
probable cause is required to search the vehicle for contraband or other evidence of a crime. And while vehicle stops at fixed
immigration checkpoints are permissible without individualized suspicion, government officers must have probable cause to
search vehicles at those checkpoints. In addition, government officers may board vessels in interior or coastal waterways to
conduct routine document and safety inspections, but may require at least reasonable suspicion to conduct more intrusive
searches of the vessel.
Recent years have seen legal challenges to border searches of electronic devices such as cell phones and computers, which
often contain more personal and sensitive information than other items frequently searched at the border, such as a wallet or
briefcase. The Supreme Court has not yet addressed this issue. Lower courts have generally held that government officers
may conduct relatively limited, manual searches of such devices without a warrant or any particularized suspicion. The
courts, however, are split over whether more intrusive, forensic searches require at least reasonable suspicion. Additionally,
there is some debate over warrantless drone surveillance at the border and surrounding areas, given a drone’s potential
capability to access more information about a person than other forms of aerial surveillance. Another emerging issue
concerns the use of biometrics, particularly the collection of DNA samples from detained aliens at the border. Apart from
these issues, there have also been concerns about the use of “racial profiling” during investigatory stops near the border.
Legislation introduced in recent Congresses would clarify the government’s ability to conduct searches and seizures at the
border and surrounding regions.
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Searches and Seizures at the Border and the Fourth Amendment
Contents
Constitutional Authority Over the Border ....................................................................................... 3
Federal Statutory and Regulatory Framework for Searches and Seizures at or Near the
Border ........................................................................................................................................... 4
Federal Customs Statutes and Regulations ............................................................................... 5
Customs Officers’ Authority ............................................................................................... 5
Coast Guard Authority ........................................................................................................ 7
Federal Immigration Laws and Regulations ............................................................................. 7
Border Searches and the Fourth Amendment ................................................................................ 12
General Overview of the Fourth Amendment ......................................................................... 12
“The People” Protected by the Fourth Amendment .......................................................... 13
Searches ............................................................................................................................ 16
Seizures ............................................................................................................................. 17
Standards of Suspicion: Probable Cause and Reasonable Suspicion ................................ 18
Warrantless Searches and Seizures ................................................................................... 19
Searches at International Borders ............................................................................................ 19
The Border and Its Functional Equivalent ........................................................................ 20
Searches and Seizures: Routine and Nonroutine .............................................................. 21
Other Exceptions to the Fourth Amendment’s Warrant Requirement That May Be
Relevant to Encounters Near the Border .............................................................................. 25
Warrantless Arrests ........................................................................................................... 27
Government Searches Beyond the Border and Its Functional Equivalent .................................... 28
Extended Border Searches ...................................................................................................... 28
Boarding and Inspection of Vessels Within Interior and Coastal Waterways ......................... 31
United States v. Villamonte-Marquez ............................................................................... 32
Lower Courts’ Decisions on Boarding of Vessels ............................................................. 33
Roving Patrols ......................................................................................................................... 34
Almeida-Sanchez v. United States .................................................................................... 35
United States v. Brignoni-Ponce ....................................................................................... 35
United States v. Cortez ...................................................................................................... 37
United States. v. Arvizu .................................................................................................... 37
Lower Court Decisions on Roving Patrols ....................................................................... 38
Fixed Immigration Checkpoints .............................................................................................. 39
United States v. Martinez-Fuerte ...................................................................................... 40
United States v. Ortiz ........................................................................................................ 41
Lower Court Decisions on Immigration Checkpoints ...................................................... 42
Transportation Checks............................................................................................................. 44
Select Legal Issues ........................................................................................................................ 45
Border Searches of Electronic Devices ................................................................................... 45
Riley v. California ............................................................................................................. 46
Lower Courts’ Application of the Border Search Exception to Electronic Device
Searches ......................................................................................................................... 46
Current CBP Policies on Electronic Device Searches ...................................................... 48
Drone Surveillance .................................................................................................................. 49
Biometric Data Collection at the Border ................................................................................. 52
Racial Profiling ....................................................................................................................... 55
Recent Legislation Concerning the Government’s Border Search Authority ............................... 59
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Figures
Figure 1. Area Within 100 Air Miles of the U.S. Border .............................................................. 10
Tables
Table A-1. Federal Statutes Authorizing Warrantless Customs Searches and Boarding of
Vessels ........................................................................................................................................ 61
Table A-2. Federal Statutes Authorizing Warrantless Searches and Seizures by
Immigration Officers .................................................................................................................. 63
Table A-3. Judicial Requirements for Border-Related Searches and Seizures .............................. 65
Appendixes
Appendix. ...................................................................................................................................... 61
Contacts
Author Information........................................................................................................................ 67
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Searches and Seizures at the Border and the Fourth Amendment
ongress has broad authority to regulate persons or items entering the United States, an
authority rooted in its power to regulate foreign commerce and to protect the integrity of
the nation’s borders.1 Acting through this authority, Congress has established a
comprehensive framework that allows federal government officers to conduct searches and
seizures of persons and property at or near the international border.2 Under federal statutes,
government officers may inspect and search individuals, merchandise, vehicles, and vessels that
are attempting to enter the United States or found further within the interior of the country shortly
after entry, including to investigate customs violations and other breaches of federal law.3
Additionally, government officers have statutory authority to investigate potential violations of
federal immigration laws at the border and surrounding areas.4
C
There are constitutional constraints on the government’s power. The Fourth Amendment to the
Constitution protects against unreasonable searches and seizures by government officers.5
Generally, the Fourth Amendment requires an officer to obtain a judicial warrant based on
probable cause before arresting or searching an individual.6 The “touchstone” of the Fourth
Amendment is reasonableness, and the reasonableness of a government search may be
determined by balancing an individual’s privacy expectations with the legitimate government
interests supporting the search.7 Thus, courts have recognized “reasonable exceptions” where the
government may engage in a warrantless arrest or search.8 For example, the government may
1 See United States v. Montoya de Hernandez, 473 U.S. 531, 538 (1985) (recognizing “Congress’ power to protect the
Nation by stopping and examining persons entering this country”); United States v. 12,200-Foot Reels of Super 8mm.
Film, 413 U.S. 123, 125 (1973) (“The Constitution gives Congress broad, comprehensive powers ‘(t)o regulate
Commerce with foreign Nations.’ Historically such broad powers have been necessary to prevent smuggling and to
prevent prohibited articles from entry.”) (quoting U.S. CONST. art. I, § 8, cl. 3.).
2 See Montoya de Hernandez, 473 U.S. at 537 (“Since the founding of our Republic, Congress has granted the
Executive plenary authority to conduct routine searches and seizures at the border, without probable cause or a warrant,
in order to regulate the collection of duties and to prevent the introduction of contraband into this country.”); United
States v. Ramsey, 431 U.S. 606, 616 (1977) (noting that Congress recognized its “plenary customs power” by enacting
the first customs statute in 1789).
3 14 U.S.C. § 522; 19 U.S.C. §§ 482, 1467, 1496, 1581, 1583.
4 8 U.S.C. § 1357.
5 Specifically, the Fourth Amendment provides that, “[t]he right of the people to be secure in their persons, houses,
papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but
upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the
persons or things to be seized.” U.S. CONST. amend. IV. This limitation applies to state officers through the Fourteenth
Amendment. Mapp v. Ohio, 367 U.S. 643, 655 (1961) (observing that the Fourth Amendment’s prohibition against
unreasonable searches and seizures extends to the states through the Due Process Clause of the Fourteenth
Amendment).
6 See Riley v. California, 134 S. Ct. 2473, 2482 (2014) (“Such a warrant ensures that the inferences to support a search
are ‘drawn by a neutral and detached magistrate instead of being judged by the officer engaged in the often competitive
enterprise of ferreting out crime.’ ”) (quoting Johnson v. United States, 333 U.S. 10, 14 (1948)); Kentucky v. King, 563
U.S. 452, 459 (2011) (“Although the text of the Fourth Amendment does not specify when a search warrant must be
obtained, this Court has inferred that a warrant must generally be secured.”).
7 United States v. Knights, 534 U.S. 112, 118–19 (2001) (“The touchstone of the Fourth Amendment is reasonableness,
and the reasonableness of a search is determined ‘by assessing, on the one hand, the degree to which it intrudes upon an
individual’s privacy and, on the other, the degree to which it is needed for the promotion of legitimate governmental
interests.’ ”) (quoting Wyoming v. Houghton, 526 U.S. 295, 300 (1999)).
8 King, 563 U.S. at 459 (“Because ‘the ultimate touchstone of the Fourth Amendment is “reasonableness” ’. . . [t]he
warrant requirement is subject to certain reasonable exceptions.”) (quoting Brigham City, Utah v. Stuart, 547 U.S. 398,
403 (2006)); Texas v. Brown, 460 U.S. 730, 735 (1983) (“Our cases hold that procedure by way of a warrant is
preferred, although in a wide range of diverse situations we have recognized flexible, common-sense exceptions to this
requirement.”).
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bypass the warrant requirement if an arrest occurs in public and is based on probable cause or if a
search is incident to a lawful arrest.9 Additionally, warrantless searches and seizures of limited
duration and intrusion, such as a “stop and frisk” of a person suspected of wrongdoing, may be
permitted under a less exacting standard than probable cause, instead requiring only reasonable
suspicion of unlawful activity.10
Citing Congress’s constitutionally enumerated power to regulate foreign commerce and the
federal government’s inherent sovereign authority to protect the nation’s borders, the Supreme
Court has held that federal law enforcement officers may engage in routine inspections and
searches at the U.S. border without a warrant, probable cause, or reasonable suspicion.11 This
“border search exception” applies in circumstances when a person is attempting to enter or is
suspected to have entered the United States at the international border.12 Federal appellate courts
have construed the border search exception as applying equally to searches of persons departing
the United States.13 The exception applies not only to the physical border itself, but also to
searches at the border’s “functional equivalent,” such as at an international airport within the
United States.14
Yet the Fourth Amendment places some limits on the government’s border search authority. The
border search exception applies at the border or its functional equivalent; searches and seizures
further into the country’s interior may require at least heightened suspicion or probable cause of
9 See Davis v. United States, 564 U.S. 229, 232 (2011) (“[A] police officer who makes a lawful arrest may conduct a
warrantless search of the arrestee’s person and the area ‘within his immediate control.’ ”) (quoting Chimel v. California,
395 U.S. 752, 763 (1969)); United States v. Watson, 423 U.S. 411, 418 (1976) (“The cases construing the Fourth
Amendment thus reflect the ancient common-law rule that a peace officer was permitted to arrest without a warrant for
a misdemeanor or felony committed in his presence as well as for a felony not committed in his presence if there was
reasonable ground for making the arrest.”).
10 See Terry v. Ohio, 392 U.S. 1, 21–22 (1968) (requiring “stop and frisk” of suspect to be predicated on “specific and
articulable facts,” rather than “unparticularized suspicion or hunch,” that “taken together with rational inferences from
those facts, reasonably warrant that intrusion.”).
11 See United States v. Flores-Montano, 541 U.S 149, 152–53 (2004) (“Time and again, we have stated that ‘searches
made at the border, pursuant to the longstanding right of the sovereign to protect itself by stopping and examining
persons and property crossing into this country, are reasonable simply by virtue of the fact that they occur at the
border.’ ”) (quoting United States v. Ramsey, 431 U.S. 606, 616 (1977)); United States v. Montoya de Hernandez, 473
U.S. 531, 538 (1985) (“Routine searches of the persons and effects of entrants are not subject to any requirement of
reasonable suspicion, probable cause, or warrant[.]”).
12 See Flores-Montano, 541 U.S. at 152 (reasoning that the government has broad authority to conduct routine searches
at the border because “[t]he Government’s interest in preventing the entry of unwanted persons and effects is at its
zenith at the international border.”); Ramsey, 431 U.S. at 619 (observing that border searches are characterized by the
fact that “the person or item in question had entered into our country from outside.”). See also D.E. v. Doe I, 834 F.3d
723, 727 (6th Cir. 2016) (search of motorist’s vehicle was lawful under the border search exception, even though the
motorist claimed to have arrived at the international border inadvertently and intended to turn around).
13 See, e.g., United States v. Odutayo, 406 F.3d 386, 391–92 (5th Cir. 2005) (holding border search exception applies to
outgoing baggage); United States v. Boumelhem, 339 F.3d 414, 419–20 (6th Cir. 2003) (establishing that border search
exception applies to outgoing cargo container); United States v. Beras, 183 F.3d 22, 26 (1st Cir. 1999) (concluding that
pat down of outgoing traveler was permitted under the border search exception).
14 Montoya de Hernandez, 473 U.S. at 538 (international airport); Ramsey, 431 U.S. at 622 (post office receiving
international mail); Almeida-Sanchez v. United States, 413 U.S. 266, 272–73 (1973) (describing the border’s functional
equivalent to include an international airport or “an established station near the border, at a point marking the
confluence of two or more roads that extend from the border”); United States v. Stewart, 729 F.3d 517, 525 (6th Cir.
2013) (international airport).
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unlawful activity.15 Moreover, a border search extending beyond a routine search may require at
least reasonable suspicion of criminal activity to withstand Fourth Amendment scrutiny.16
This report examines the statutory framework for border searches and seizures and the
constitutional constraints that must inform the exercise of this statutory authority. The report first
surveys federal statutes and regulations authorizing government officers to conduct warrantless
searches and seizures at the border and surrounding areas. The report then discusses the Fourth
Amendment’s general limitations on government searches and seizures. The report next examines
the border search exception and the extension of that exception further into the interior of the
United States, such as at immigration checkpoints on roads near the border. The report also
discusses several emerging border-related Fourth Amendment issues, including electronic device
searches at the border, drone surveillance, the collection of biometric data, and racial profiling.
Finally, the report reviews recent legislation concerning the government’s border search authority.
Constitutional Authority Over the Border
The Supreme Court has long recognized the authority of government officials to perform searches
and seizures at international borders.17 The Court has traced this federal power to two sources: (1)
the United States’ inherent sovereignty as a nation-state;18 and (2) the Constitution’s Foreign
Commerce Clause.19
By establishing a federal government, the Constitution was understood to confer upon it all the
powers incident to the United States’ existence as a sovereign, independent nation—including
unqualified authority over the nation’s borders and ability to determine whether foreign nationals
may come within its territory.20 The Supreme Court has repeatedly recognized that principles of
15
See United States v. Martinez-Fuerte, 428 U.S. 543, 562 (1976) (holding that routine checkpoint stops near the
border do not require any individualized suspicion); United States v. Brignoni-Ponce, 422 U.S. 873, 884 (1975)
(“Except at the border and its functional equivalents, officers on roving patrol may stop vehicles only if they are aware
of specific articulable facts, together with rational inferences from those facts, that reasonably warrant suspicion that
the vehicles contain aliens who may be illegally in the country.”); Almeida-Sanchez, 413 U.S. at 273 (holding that
“roving patrol” search of automobile more than 20 miles north of the U.S.-Mexico border required probable cause or
consent); Alfonso, 759 F.2d at 734 (requiring reasonable suspicion for extended border searches occurring subsequent
to a border crossing).
16 See Flores-Montano, 541 U.S. at 152–54, 156 (suggesting that “highly intrusive” searches of a person or
“destructive” searches of property may require a heightened level of suspicion); Montoya de Hernandez, 473 U.S.
at 541 (“We hold that the detention of a traveler at the border, beyond the scope of a routine customs search and
inspection, is justified at its inception if customs agents, considering all the facts surrounding the traveler and her trip,
reasonably suspect that the traveler is smuggling contraband in her alimentary canal.”).
17 See, e.g., Montoya de Hernandez, 473 U.S. at 537; Ramsey, 431 U.S. at 616; Carroll v. United States, 267 U.S. 132,
154 (1925).
18 See, e.g., Ramsey, 431 U.S. at 616 (“That searches made at the border, pursuant to the long-standing right of the
sovereign to protect itself by stopping and examining persons and property crossing into this country, are reasonable
simply by virtue of the fact that they occur at the border, should, by now, require no extended demonstration.”);
Carroll, 267 U.S. at 154.
19 Ramsey, 431 U.S. at 619.
20 See, e.g., Chae Chan Ping v. United States, 130 U.S. 581, 609 (1889) (recognizing “[t]he power of exclusion of
foreigners” as “an incident of sovereignty belonging to the United States as a part of those sovereign powers delegated
by the constitution”); Nishimura Ekiu v. United States, 142 U.S. 651, 659 (1892) (“It is an accepted maxim of
international law that every sovereign nation has the power, as inherent in sovereignty, and essential to selfpreservation, to forbid the entrance of foreigners within its dominions, or to admit them only in such cases and upon
such conditions as it may see fit to prescribe.”); see also United States v. Curtiss-Wright, 299 U.S. 304, 318 (1936)
(“The power to acquire territory by discovery and occupation, the power to expel undesirable aliens, the power to make
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sovereignty include giving the federal government the power to regulate items and persons
entering U.S. territory.21 The Court has explained: “It is axiomatic that the United States, as
sovereign, has the inherent authority to protect, and a paramount interest in protecting, its
territorial integrity.”22 The Court observed in dicta in Carroll v. United States that “[t]ravelers
may be stopped in crossing an international boundary because of national self-protection
reasonably requiring one entering the country to identify himself as entitled to come in, and his
belongings as effects which may be lawfully brought in.”23
Authority to search items and persons at international borders has also been traced to the Foreign
Commerce Power, which grants Congress broad authority to regulate commerce with foreign
nations.24 The Court has described searches at the international border as “necessary to prevent
smuggling and to prevent prohibited articles from entry.”25
Federal Statutory and Regulatory Framework for
Searches and Seizures at or Near the Border
Federal statutes and implementing regulations confer designated law enforcement officers with
broad authority to conduct searches and seizures at the border and surrounding areas without a
warrant. These searches commonly occur at designated ports of entry along the border, such as
border crossing points.26 But searches may also occur in other places along or near the border.27
To enforce U.S. customs laws, federal law enforcement officers may inspect and search
individuals, merchandise, vehicles, and vessels arriving at the border, as well as further into the
interior of the United States and within U.S. waters. In addition, federal officers may detain and
such international agreements as do not constitute treaties in the constitutional sense, none of which is expressly
affirmed by the Constitution, nevertheless exist as inherently inseparable from the conception of nationality.”).
21 See, e.g., Ramsey, 431 U.S. at 616 (“That searches made at the border, pursuant to the long-standing right of the
sovereign to protect itself by stopping and examining persons and property crossing into this country, are reasonable
simply by virtue of the fact that they occur at the border, should, by now, require no extended demonstration.”);
Carroll, 267 U.S. at 154. Sovereignty, as a general principle, stems from a global recognition of international rules
governing the authority of a nation-state and its interactions with other nation-states. Sarah H. Cleveland, Powers
Inherent in Sovereignty: Indians, Aliens, Territories and the Nineteenth Century Origins of Plenary Power over
Foreign Affairs, 81 TEX. L. REV. 1, 15 (2002); see also Curtiss-Wright, 299 U.S. at 318 (“As a member of the family of
nations, the right and power of the United States in that field are equal to the right and power of the other members of
the international family.”).
21 Ramsey, 431 U.S. at 619.
22 United States v. Flores-Montano, 541 U.S. 149, 153 (2004).
23 Carroll, 267 U.S. at 154; see also Boyd v. United States, 116 U.S. 616 (1886).
24 U.S. CONST. art. I, § 8, cl. 3 (granting Congress “the power . . . [t]o regulate Commerce with foreign Nations[.]”).
25 United States v. Montoya de Hernandez, 473 U.S. 531, 537–38 (1985) (involving an individual stopped at airport
suspected of smuggling narcotics).
26 See United States v. Cotterman, 709 F.3d 952, 961–62 (9th Cir. 2013) (describing a “border search” as one that
occurs at ports of entry where there is an actual or attempted border crossing); U.S. CUSTOMS AND BORDER
PROTECTION, Border Security: At Ports of Entry (last modified Apr. 2, 2018), https://www.cbp.gov/bordersecurity/ports-entry (describing U.S. Customs and Border Protection’s functions at ports of entry).
27 See United States v. Villamonte-Marquez, 462 U.S. 579, 593 (1983) (recognizing the government’s interest in
patrolling inland or coastal waters “where the need to deter or apprehend smugglers is great”); Almeida-Sanchez v.
United States, 413 U.S. 266, 268 (1973) (noting that the Border Patrol conducts inland surveillance activities “all in the
asserted interest of detecting the illegal importation of aliens.”); U.S. Customs & Border Prot., Border Security: Along
U.S. Borders (Jan. 17, 2018), https://www.cbp.gov/border-security/along-us-borders (describing the Border Patrol’s
responsibilities along the border).
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search individuals and their vehicles at or near the border to enforce federal immigration laws.
Federal officers may also enforce other laws relating to the border, including federal statutes
concerning transnational criminal activity (e.g., gang activity), the introduction of harmful plant
or animal species, and public health requirements.28
Federal Customs Statutes and Regulations
Title 19 of the U.S. Code regulates commerce and the flow of goods into the United States.29 It
authorizes customs officers to inspect and search individuals and their personal belongings,
merchandise, vehicles, vessels, and other means of transport for the purpose of searching for
contraband and other violations of federal customs laws.30 This authority is encompassed in
various federal statutes, some of which are overlapping in scope. U.S. Customs and Border
Protection (CBP), a component of the Department of Homeland Security (DHS),31 is the federal
agency mainly responsible for enforcing customs laws.32 The U.S. Coast Guard also has customs
enforcement authority.33
Customs Officers’ Authority
Under 19 U.S.C. § 1496, a customs officer34 may examine “the baggage of any person arriving in
the United States in order to ascertain what articles are contained therein” and whether those
items are subject to taxes or otherwise prohibited.35 Similarly, 19 U.S.C. §1467 allows customs
officers to inspect and search the persons, baggage, and merchandise arriving by vessel from a
foreign port (including U.S. territories).36 Federal regulations also state that “[a]ll persons,
See, e.g., U.S. Immigr. & Customs Enf’t, Homeland Security Investigations (Aug. 15, 2019),
https://www.ice.gov/hsi; U.S. Customs & Border Prot., Protecting Agriculture (June 10, 2019),
https://www.cbp.gov/border-security/protecting-agriculture.
29 See 19 U.S.C. §§ 1–4732.
30 See id. §§ 482, 1467, 1496, 1499, 1581, 1582, 1583. Certain diplomatic officers and their families are exempted from
Title 19’s search authority. 19 C.F.R. § 148.82.
31 DHS’s predecessor agency, the former Immigration and Naturalization Service (INS), ceased to exist as an
independent agency under the U.S. Department of Justice in 2003, and its functions were transferred to DHS. See
Homeland Security Act of 2002, Pub. L. No. 107-296, §§ 101, 441, 451, 471, 116 Stat. 2135, 2142, 2192, 2195, 2205
(2002).
32 See 6 U.S.C. § 202 (delegating to the Secretary of Homeland Security responsibility for “administering the customs
laws of the United States.”); id. § 211(c) (authorizing the CBP Commissioner to regulate the flow of travelers and
goods entering or exiting the United States, and to enforce customs and trade laws). DHS assumed responsibilities that
were transferred from various federal agencies. See id. § 203. DHS’s customs enforcement responsibilities, carried out
by CBP, derive from the U.S. Customs Service of the Department of Treasury. Id. § 203(1). DHS’s immigration
enforcement functions, which are carried out by CBP and a separate component, U.S. Immigration and Customs
Enforcement, derive from the former INS. Id. § 251.
33 19 U.S.C. § 1709(b).
34 See id. (“The term ‘officer of the customs’ means any officer of the Customs Service or any commissioned, warrant,
or petty officer of the Coast Guard, or agent or other person authorized by law or by the Secretary of the Treasury, or
appointed in writing by a collector, to perform the duties of an officer of the Customs Service.”); 19 C.F.R. § 101.1
(“The terms ‘Customs’ or ‘U.S. Customs Service’ mean U.S. Customs and Border Protection.”).
35 19 U.S.C. § 1496; see also id. § 1583(a)(1) (authorizing the warrantless search of international mail).
36 Id. § 1467; see also id. § 1499 (providing that imported merchandise subject to inspection generally shall remain in
“customs custody” until it has been inspected and is found to have been “truly and correctly invoiced and found to
comply with the requirements of the laws of the United States”).
28
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baggage, and merchandise arriving in the Customs territory of the United States from places
outside thereof are liable to inspection and search by a Customs officer.”37
Title 19 also authorizes the boarding of vehicles and vessels.38 Under 19 U.S.C. § 1581, customs
officers may board “any vessel or vehicle at any place in the United States or within the customs
waters” to “examine the manifest and other documents and papers,” or to “examine, inspect, and
search the vessel or vehicle and every part thereof and any person, trunk, package, or cargo on
board.”39 The statute defines “customs waters” to include areas within 4 leagues (i.e., 12 nautical
miles) of the U.S. coast.40 The statute also authorizes customs officers to seize any vessel or
vehicle that is subject to forfeiture, fine, or penalty.41 The statute permits the boarding of vessels
found anywhere in the United States or within customs waters, even if the vessel is not believed
to be coming from a foreign port.42
19 U.S.C. § 482 permits customs officers who have authority to board vessels to search “any
vehicle, beast, or person” suspected of carrying merchandise that is subject to customs duties or
that has been brought into the United States “in any manner contrary to law.”43 The statute
authorizes the officers to “search any trunk or envelope” for which there is “reasonable cause to
suspect there is merchandise which was imported contrary to law.”44
37 19 C.F.R. § 162.6; see also id. § 101.1 (“‘Customs territory of the United States’ includes only the States, the District
of Columbia, and Puerto Rico.”).
38 See 19 U.S.C. § 1401(a) (“The word ‘vessel’ includes every description of water craft or other contrivance used, or
capable of being used, as a means of transportation in water, but does not include aircraft.”), (j) (“The word ‘vehicle’
includes every description of carriage or other contrivance used, or capable of being used, as a means of transportation
on land, but does not include aircraft.”); United States v. Gonzalez, 688 F. Supp. 658, 664 (D.D.C. 1988) (“In 1935,
Congress passed the Anti-Smuggling Act (‘Act’), which significantly amended many of the Customs Service laws to
expand the agency’s jurisdiction to board vessels in international waters.”).
39
19 U.S.C. § 1581(a).
40 See id. §§ 1401(j), 1709(c) (“The term ‘customs waters’ means, in the case of a foreign vessel subject to a treaty or
other arrangement between a foreign government and the United States enabling or permitting the authorities of the
United States to board, examine, search, seize, or otherwise to enforce upon such vessel upon the high seas the laws of
the United States, the waters within such distance of the coast of the United States as the said authorities are or may be
so enabled or permitted by such treaty or arrangement and, in the case of every other vessel, the waters within four
leagues of the coast of the United States.”).
41 Id. § 1581(e); see also id. § 1595(a)(1) (providing that, if the customs officer has probable cause that any of the
merchandise or property is in a “dwelling house, store, or other building place,” he or she may seek a judicial warrant
authorizing entry into the house (during daytime only) or store or other building to search for and seize the
merchandise).
42 Federal regulations similarly provide that customs officers may board a vessel anywhere in the United States or
within “customs waters”; an American vessel on the high seas; or a vessel within a “customs-enforcement area” (an
area on the high seas adjacent to customs waters where a vessel is being kept to prevent the unlawful importation of
persons or merchandise) to inspect the vessel and review documentation. 19 C.F.R. § 162.3(a); 19 U.S.C. § 1701(a).
But “Customs officers shall not board a foreign vessel upon the high seas in contravention of any treaty with a foreign
government, or in the absence of a special arrangement with the foreign government concerned.” 19 C.F.R. § 162.3(a).
See also id. § 162.5 (“A customs officer may stop any vehicle and board any aircraft arriving in the United States from
a foreign country for the purpose of examining the manifest and other documents and papers and examining,
inspecting, and searching the vehicle or aircraft.”).
43 19 U.S.C. § 482(a); see also 19 C.F.R. § 162.7 (“A Customs officer may stop, search, and examine any vehicle,
person, or beast, or search any trunk or envelope wherever found, in accordance with section 3061 of the Revised
Statutes (19 U.S.C. 482).”).
44 19 U.S.C. § 482(a). The Supreme Court has held that the statute permits customs officers to inspect incoming
international mail if there is “reasonable cause” that it contains unlawfully imported merchandise. United States v.
Ramsey, 431 U.S. 606, 611–12 (1977). The Court described the statute’s “reasonable cause” standard as being “less
stringent” that than the probable cause standard that generally applies to government searches under the Fourth
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Additionally, under 19 U.S.C. § 1589a, customs officers may make warrantless arrests for any
criminal offense under federal law that is committed in the officers’ presence; or for any felony
under federal law that is committed outside the officers’ presence if the officers have reasonable
grounds to believe the suspect has committed the felony.45
Coast Guard Authority
Title 14 of the U.S. Code sets forth powers exclusive to the Coast Guard.46 Under 14 U.S.C. §
522, Coast Guard officers may stop and board any vessel on “the high seas and waters over which
the United States has jurisdiction,” so long as the vessel is “subject to the jurisdiction, or to the
operation of any law, of the United States.”47 Unlike 19 U.S.C. § 1581, the statute’s reach extends
beyond the United States’ customs waters to the “high seas,” defined as “all parts of the sea that
are not included in the territorial sea or in the internal waters of any nation.”48 Under the statute,
Coast Guard officers may question a vessel’s occupants, examine documentation, and conduct
inspections and searches of the vessel to investigate potential violations of federal law.49 The
statute also permits officers to arrest for violations of federal law (including arresting an
individual escaping from the vessel to shore), and to seize any vessel or merchandise involved in
criminal activity.50
A table comparing federal statutes authorizing warrantless searches by customs officers generally,
and those pertaining to the search and boarding authority specific to the Coast Guard, can be
found in the Appendix at Table A-1.
Federal Immigration Laws and Regulations
DHS is the federal agency primarily charged with the administration and enforcement of
immigration laws.51 Within DHS, CBP is the agency component mainly responsible for
immigration enforcement along the border and at designated ports of entry52 and typically
Amendment. Id. at 612 ̶ 13.
45 19 U.S.C. § 1589a(3).
46 See 14 U.S.C. Subpt. I, Ch. 5. The Coast Guard also has authority to enforce customs laws under Title 19 of the U.S.
Code (discussed above). 19 U.S.C. § 1709(b). Previously part of the Department of Transportation, the Coast Guard is
now an entity housed within DHS. See 6 U.S.C. § 468(b). During wartime, the Coast Guard can be transferred to the
Department of Navy upon direction from either Congress or the President. 14 U.S.C. § 103(b). This section, however,
only discusses the statutory authorities applicable to the Coast Guard in its role in maritime law enforcement, and does
not address other authorities that might be applicable in a wartime context.
47 Id. § 522(a). The phrase “subject to the jurisdiction, or to the operation of any law, of the United States” does not
cover only American flag vessels. United States v. Williams, 617 F.2d 1063, 1076 (5th Cir. 1980). It also covers
foreign vessels on the high seas that are engaged in criminal offenses that have an effect on U.S. sovereign territory
(e.g., a conspiracy to violate federal narcotics laws). Id. (citing United States v. Cadena, 585 F.2d 1252, 1257 (5th Cir.
1978)).
48 33 U.S.C. § 1601. The “territorial sea” of the United States is defined as the area within 12 nautical miles of the U.S.
coastline (i.e., the customs waters). Id. § 3507.
49 14 U.S.C. § 522(a).
50 Id.; see also 46 U.S.C. § 70503(a) (prohibiting the manufacture or distribution of, or the possession with intent to
manufacture or distribute, a controlled substance on board a vessel).
51 See Homeland Security Act of 2002, Pub. L. No. 107-296, § 101(a), 116 Stat. 2135 (2002) (codified at 6 U.S.C.
§ 111(a)). As discussed in this report, DHS’s immigration enforcement functions derive from the former INS. 6 U.S.C.
§ 251.
52 See id. § 211(c) (listing functions of CBP).
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conducts immigration inspections and arrests in border regions.53 U.S. Immigration and Customs
Enforcement (ICE)—the DHS component tasked with interior enforcement and removal—may
also cooperate with CBP, such as in investigating cross-border criminal activity (e.g., human
trafficking, gang activity, drug smuggling).54
The Immigration and Nationality Act (INA)55 authorizes immigration officers to conduct searches
and seizures.56 This authority generally concerns the investigation of immigration violations, such
as the search of aliens suspected of unlawfully entering the country, but also generally permits the
arrest of persons (including U.S. citizens) who engage in certain criminal activity discovered
within the course of the officer’s duties.57
Under Section 287 of the INA, an immigration officer may conduct, under the terms of
regulations prescribed by the Secretary of DHS, several types of immigration enforcement actions
without a warrant,58 including at the border and surrounding areas.59 Under INA Section
287(a)(1), an immigration officer may, under the terms of prescribed regulations, “interrogate any
alien or person believed to be an alien as to his right to be or to remain in the United States.”60
DHS regulations similarly state that the officer may ask anyone questions so long as the officer
“does not restrain the freedom of an individual, not under arrest, to walk away.”61
INA Section 287(a)(3) provides that, “within a reasonable distance from any external boundary of
the United States,” an immigration officer may “board and search for aliens any vessel within the
territorial waters of the United States and any railway car, aircraft, conveyance, or vehicle” to
enforce federal immigration laws.62
DHS regulations define “external boundary” as “the land boundaries and the territorial sea of the
United States extending 12 nautical miles (i.e., roughly 13.8 land miles) from the baselines of the
United States determined in accordance with international law.”63
“Reasonable distance” is defined as “within 100 air miles (i.e., roughly 115 land miles) from any
external boundary of the United States” or “any shorter distance” set by the chief patrol agent of
53 Within CBP, the Office of Field Operations is the agency component that conducts inspections and enforces
immigration and customs laws at designated ports of entry. See id. § 211(g)(3). The U.S. Border Patrol is the CBP
component primarily charged with the apprehension of aliens unlawfully entering the United States or who have
recently entered the country unlawfully away from a designated point of entry; as well as the interdiction of goods that
are unlawfully imported into the United States. See id. § 211(e)(3).
54 See U.S. Immigr. & Customs Enf’t, Homeland Security Investigations (Jan. 8, 2020), http://www.ice.gov/about.
55 Immigration and Nationality Act of 1952, Pub. L. No. 82-414, 66 Stat. 163 (1952).
56 See id. § 287(a), (c) (codified at 8 U.S.C. § 1357(a), (c)); see also 8 C.F.R. §§ 287.1, 287.5 (implementing
regulations).
57 8 U.S.C. §§ 1225(a)(3), 1225(d)(1), 1357(a), (c).
58 Generally, an immigration officer must have an administrative “Warrant of Arrest” (Form I-200) to arrest and detain
an alien who is subject to removal from the United States. 8 U.S.C. § 1226(a); 8 C.F.R. § 236.1(b).
59 8 U.S.C. § 1357(a), (c); 8 C.F.R. §§ 287.1, 287.3, 287.5, 287.8.
60 8 U.S.C. § 1357(a)(1).
61 8 C.F.R. § 287.8(b)(1). But the officer may “briefly detain” an individual if he or she has reasonable suspicion that
the person being questioned is committing a crime or is unlawfully present in the United States. Id. § 287.8(b)(2).
62 8 U.S.C. § 1357(a)(3); see also id. § 1225(d)(1) (“Immigration officers are authorized to board and search any vessel,
aircraft, railway car, or other conveyance or vehicle in which they believe aliens are being brought into the United
States.”).
63 8 C.F.R. § 287.1(a)(1).
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CBP or special agent of ICE for a particular sector or district.64 Factors that may be considered
when setting a distance within this area include topography, confluence of arteries of
transportation leading from external boundaries, density of population, potential inconvenience to
the public, types of conveyances used, and reliable information about the movement of persons
who are unlawfully entering the United States.65 Additionally, the regulations provide the
possibility that, in “unusual circumstances,” a distance beyond 100 air miles from the border may
be deemed “reasonable.”66 For that to occur, the chief patrol agent or special agent must “forward
a complete report with respect to the matter to the Commissioner of CBP, or the Assistant
Secretary for ICE, as appropriate, who may, if he determines that such action is justified, declare
such distance to be reasonable.”67
Figure 1 shows a map of the area within 100 air miles of an external boundary of the United
States (shaded in pink), along with the factors considered by DHS in assessing whether a greater
or shorter distance may be set for particular sectors.
64 Id. § 287.1(a)(2). For boarding and searching aircraft, agency officials may set “any distance.” Id.
65 Id. § 287.1(b).
66 Id.
67 Id.
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Figure 1. Area Within 100 Air Miles of the U.S. Border
Factors Considered in Setting Distances Within 100-Air Mile Area*
Topography
Types of
conveyances
used
Confluence of arteries of
transportation leading from
external boundaries
Density of population
Possible inconvenience to the traveling
public
Reliable information as to
movements of persons effecting
unlawful entry into the United
States
* Unusual circumstances (may be considered in
setting distances greater than 100 air miles)
Source: Congressional Research Service; 8 C.F.R. § 287.1(a)(2), (b).
Note: This figure includes cities located within 100 miles of the country’s external boundary with a population
greater than 500,000 persons.
Although INA Section 287(a)(3) and implementing regulations give immigration officers broad
authority to conduct warrantless searches near the border, as will be discussed later in the report,
the Constitution sets limits on how this authority may be implemented.68 For that reason, the
government’s search authority along the border is not unfettered, and immigration officers’ ability
to conduct warrantless searches near the border are informed by a number of factors, including
population density and inconvenience to the public.69 Thus, the ability to conduct warrantless
searches in desolate border regions does not necessarily mean that such authority equally extends
to populated metropolitan areas near the border.70
68 See infra “Government Searches Beyond the Border and Its Functional Equivalent.”
69 8 C.F.R. § 287.1(b).
70 See Petition for Writ of Certiorari, Almeida-Sanchez v. United States, 413 U.S. 266 (1973) (No. 71-6278) (“Despite
the apparently unlimited authority the language of the statute seems to convey to board and search within a ‘reasonable
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Apart from authorizing searches near the border, INA Section 287(a)(3) authorizes certain
designated immigration officers “to have access to private lands” (but not dwellings) within 25
miles71 from any external boundary of the United States for the purpose of “patrolling the
border.”72 Under DHS regulations, “patrolling the border” means “conducting such activities as
are customary, or reasonable and necessary, to prevent the illegal entry of aliens into the United
States.”73 The U.S. Court of Appeals for the Ninth Circuit (Ninth Circuit)74 has held that INA
Section 287(a)(3)’s restriction on access to “dwellings” on private lands applies to homes,
including the residential curtilage (e.g., a backyard).75 The court reasoned that if “dwellings” was
narrowly interpreted to cover only a home’s physical structure, immigration officers would have
the “unchecked ability” to enter any private backyard near the border, so long as they did not
enter the physical structure itself.76 The court opined that it would be unreasonable to assume that
Congress intended to confer such “broad and sweeping powers” given the potential constitutional
issues raised by such a narrow construction of the statute.77
Under INA Section 287(a)(2), designated immigration officers may arrest an alien without a
warrant if (1) the alien is entering or trying to enter the United States unlawfully in the presence
or view of the officer; or (2) there is “reason to believe” the alien is unlawfully in the United
distance’ of the border, the statute has never been understood to permit arbitrary searches and has not been used as a
pretext to search for evidence of other criminal conduct. Thus, the establishment of checkpoints within the 100-mile
maximum fixed by regulation, 8 C.F.R. 287.1 (a)(2), is based upon a consideration of various factors designed to
accomplish the statutory objective with the least possible intrusion upon the privacy of travelers. Hence, as illustrated
by the present case, the INS has not claimed and would not claim statutory or constitutional authority to make random
vehicle inspections for aliens in Times Square or in front of the Lincoln Memorial, even though technically these points
are within 100 air miles of an external border. There is, quite simply, not a sufficient need for such operations to justify
the inconvenience they would cause, and thus they would be ‘unreasonable’ in the constitutional sense. But vehicle
checks conducted in areas where the incidence of illegal entry and alien smuggling is high are, if executed in good faith
and with minimum inconvenience to the traveling public, reasonable within the Fourth Amendment.”).
71 The statutory provision setting forth immigration officers’ ability to have access to private lands within a distance of
25 miles from an external U.S. boundary, 8 U.S.C. § 1357(a)(3), does not specify whether this measurement is in
statute miles (5,280 feet) typically used in land measurement or air/nautical miles (roughly 6,076.115 feet). Compare
Mile, Statute Mile, and Nautical Mile, BLACK’S LAW DICTIONARY (11th ed. 2019). The provision’s application to
searches arising on land would support construing “twenty-five miles” to mean 25 statute miles. Cf. Buttimer v. Detroit
Sulphite Transp. Co., 39 F. Supp. 222, 227 (E.D. Mich. 1941) (provision of Seamen’s Act concerning voyages of less
than “600 miles” meant nautical miles, because “it is presumed, unless otherwise specified, that distances on water
refer to nautical rather than land miles”). Related regulations concerning the powers and duties of immigration officers
do not provide further guidance, though two other terms used in the same statutory provision, relating to the “external
boundary” of the United States and a “reasonable distance” from that external boundary, are defined using air/nautical
mileage. 8 C.F.R. § 287.1(a)-(b).
72 8 U.S.C. § 1357(a)(3); 8 C.F.R. § 287.5(b). Under CBP policy, the officer must inform the owner or occupants of the
private lands that he or she intends to access those lands. See U.S. CUSTOMS & BORDER PROT., INSPECTOR’S FIELD
MANUAL § 18.6(d).
73 8 C.F.R. § 287.1(c).
74 This report references a number of decisions by federal appellate courts of various regional circuits. For purposes of
brevity, references to a particular circuit in the body of this report (e.g., the Ninth Circuit) refer to the U.S. Court of
Appeals for that particular circuit.
75 United States v. Romero-Bustamente, 337 F.3d 1104, 1110 (9th Cir. 2003).
76 Id. at 1109 (“Nonetheless, there are good reasons to eschew the plain meaning interpretation here, because it would
indeed work an absurd result. Excluding only dwellings, in the most restricted literal sense, from the Border Patrol’s
warrantless search authority would provide its agents the unchecked ability to enter every backyard in metropolitan San
Diego, Detroit, Buffalo, and El Paso, all of which are well within 25 miles of external borders of the United States.
Aside from the obvious constitutional implications of such an interpretation, we seriously doubt that Congress intended
to give the Border Patrol such unique and sweeping powers.”).
77 Id.
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States and likely to escape before a warrant can be obtained.78 INA Section 287(a) also permits
designated immigration officers to make warrantless arrests for criminal offenses in specified
circumstances (e.g., when the offense is committed in the officer’s presence, or there is “reason to
believe” the suspect committed a felony and would likely escape).79
INA Section 287(c) authorizes designated immigration officers to conduct a warrantless search of
a person who is seeking admission to the United States (and his or her personal belongings).80
There must be “reasonable cause” to suspect there are grounds for denying the person’s
admission that the search would disclose.81
A table listing INA provisions that authorize warrantless searches and seizures by immigration
officers can be found in Table A-2.
Border Searches and the Fourth Amendment
Although federal statute and implementing regulations provide designated government officers
with broad authority to conduct warrantless searches and seizures along or near international
borders for specified purposes, including to deter immigration and customs violations, there are
constitutional constraints to the exercise of this authority—the most notable being the Fourth
Amendment.82 This section provides a brief overview of Fourth Amendment concepts and then
examines how these concepts apply to searches and seizures conducted at or near the border.
Besides discussing the scope and reach of the border search exception, this section also briefly
identifies several other exceptions to generally applicable warrant requirements that may be
relevant to law enforcement encounters near the border.
General Overview of the Fourth Amendment
The Fourth Amendment protects against unreasonable searches and seizures by government
actors.83 It provides:
The right of the people to be secure in their persons, houses, papers, and effects, against
unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but
upon probable cause… and particularly describing the place to be searched, and the persons
or things to be seized.84
78 8 U.S.C. § 1357(a)(2); 8 C.F.R. § 287.5(c)(1). Courts have viewed the “reason to believe” standard as equivalent to
probable cause. See Morales v. Chadbourne, 793 F.3d 208, 216 (1st Cir. 2015); United States v. Quintana, 623 F.3d
1237, 1239 (8th Cir. 2010); Tejeda-Mata v. INS, 626 F.2d 721, 725 (9th Cir. 1980); United States v. Cantu, 519 F.2d
494, 496 (7th Cir. 1975); Au Yi Lau v. INS, 445 F.2d 217, 222 (D.C. Cir. 1971).
79 8 U.S.C. § 1357(a)(4), (5); 8 C.F.R. § 287.5(c)(2)-(4).
80
8 U.S.C. § 1357(c); 8 C.F.R. § 287.5(d).
81 8 U.S.C. § 1357(c).
82 See, e.g., United States v. Brignoni-Ponce, 422 U.S. 873, 882–83 (1975) (statute giving immigration officers the
power to conduct warrantless searches within a “reasonable distance” of the border must be construed against the
backdrop of the Fourth Amendment); United States v. Nichols, 142 F.3d 857, 864–68 (5th Cir. 1998) (observing that
statutory authority of immigration officers to conduct searches within a “reasonable distance” of the border are subject
to the Fourth Amendment’s reasonableness requirements, and describing circuit case law as recognizing that searches
occurring more than 50 miles from the border are usually considered as being a “substantial distance” from the border)
(internal citation omitted).
83 U.S. CONST. amend. IV.
84 Id.
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The first portion of the Fourth Amendment, sometimes called the Reasonableness Clause,
enumerates what the amendment seeks to prohibit. It specifies that “the people” are protected;
that “persons, houses, papers, and effects” are covered; and the nature of the protection (“to be
secure . . . against unreasonable searches and seizures”). The second portion, sometimes called
the Warrant Clause, sets forth the requirements for a warrant to be issued, including “probable
cause” that a search will uncover evidence of wrongdoing.85
“The People” Protected by the Fourth Amendment
The Fourth Amendment secures the right of “the people” to be free from unreasonable searches
and seizures. At times, the Supreme Court has suggested that the category of individuals protected
by the Fourth Amendment is not coextensive with the category protected by the Fifth
Amendment, which applies to every “person” in the United States.86 In United States v. VerdugoUrquidez, the Supreme Court held that a foreign national arrested at his residence in Mexico and
involuntarily brought to the United States to stand trial did not come within the protective scope
of the Fourth Amendment.87 Writing for the Court, Chief Justice Rehnquist observed:
“[T]he people” seems to have been a term of art employed in select parts of the
Constitution. The Preamble declares that the Constitution is ordained and established by
“the People of the United States.” The Second Amendment protects “the right of the people
to keep and bear Arms,” and the Ninth and Tenth Amendments provide that certain rights
and powers are retained by and reserved to “the people.” See also U.S. CONST., Amdt. 1
(“Congress shall make no law . . . abridging . . . the right of the people peaceably to
assemble”) (emphasis added); Art. I, § 2, cl. 1 (“The House of Representatives shall be
composed of Members chosen every second Year by the People of the several States”)
(emphasis added). While this textual exegesis is by no means conclusive, it suggests that
“the people” protected by the Fourth Amendment, and by the First and Second
Amendments, and to whom rights and powers are reserved in the Ninth and Tenth
Amendments, refers to a class of persons who are part of a national community or who
have otherwise developed sufficient connection with this country to be considered part of
that community. . . .The language of these Amendments contrasts with the words “person”
and “accused” used in the Fifth and Sixth Amendments regulating procedure in criminal
cases.88
85 Id. See generally Illinois v. Gates, 462 U.S. 213, 231–38 (1983).
86 U.S. CONST. amend. V (providing that no “person” may be denied due process and other enumerated protections);
United States v. Verdugo-Urquidez, 494 U.S. 259, 265–66 (1990). See also Zadvydas v. Davis, 533 U.S. 678, 693
(2001) (“[T]he Due Process Clause applies to all “persons” within the United States, including aliens, whether their
presence here is lawful, unlawful, temporary, or permanent.”).
87 Verdugo-Urquidez, 494 U.S. at 274–75.
88 Id. at 265. Chief Justice Rehnquist’s opinion was joined by Justices Kennedy, O’Connor, Scalia, and Thomas. But
Justice Kennedy, who provided a critical vote to make the majority, also issued a concurring opinion indicating some
disagreement with the Chief Justice’s analysis. Id. at 275 (Kennedy, J.). While Justice Kennedy wrote that he “joined
the opinion of the Court” and believed “no violation of the Fourth Amendment occurred” in the present case, he
explained that he did not “place any weight on the reference to ‘the people’ in the Fourth Amendment as a source of
restricting its protections.” Id. at 275–276. Instead, Justice Kennedy believed the case turned primarily on the Fourth
Amendment’s extraterritorial application, which he characterized as a context-specific inquiry. Id at 277–78. This has
prompted some to describe Chief Justice Rehnquist’s opinion in Verdugo-Urquidez, at least with respect to its analysis
of “the people” protected by the Fourth Amendment, as reflecting the views of a plurality of the Court rather than a
five-Justice majority. See, e.g., The Hon. Karen Nelson Moore, Aliens and the Constitution, 88 N.Y.U. L. REV. 801,
808 (2013) (“[A] plurality led by Chief Justice Rehnquist declared that the expression ‘“the people” seems to have been
a term of art employed in select parts of the Constitution’ that extends certain rights to ‘a class of persons who are part
of a national community or who have otherwise developed sufficient connection with this country to be considered part
of that community.’ ”) (quoting Verdugo-Urquidez, 494 U.S. at 265). In any event, later courts have generally viewed
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In the years since Verdugo-Urquidez was decided, there appears to be little dispute that U.S.
citizens and lawfully present, resident aliens fall within the Fourth Amendment’s protective
scope.89 And in 2020, citing Verdugo-Urquidez and other cases, the Court declared that “it is long
settled as a matter of American constitutional law that foreign citizens outside U. S. territory do
not possess rights under the U. S. Constitution.”90 But there is less clarity regarding the Fourth
Amendment’s application to other categories of aliens, particularly those who are unlawfully
present in the United States.91
Some Supreme Court cases prior to Verdugo-Urquidez suggest that unlawfully present aliens are
among “the people” protected by the Fourth Amendment.92 For instance, Chief Justice
Rehnquist’s opinion in Verdugo-Urquidez acknowledged that in INS v. Lopez-Mendoza “a
majority of Justices assumed that the Fourth Amendment applied to illegal aliens in the United
States.”93 But the Chief Justice characterized that assumption as nonbinding dicta,94 and described
earlier Court decisions as “not dispositive on how the Court would rule on a Fourth Amendment
claim” brought by an unlawfully present alien.95
In the years since Verdugo-Urquidez, it appears that the majority of reviewing courts have held or
assumed that the Fourth Amendment applies to at least some unlawfully present aliens within the
United States.96 But some courts have concluded that some unlawfully present aliens do not
the framework set forth by the Chief Justice as controlling. See, e.g., United States v. Mesa-Rodriguez, 798 F.3d 664,
670 (2d Cir. 2015) (“At a minimum, Verdugo–Urquidez governs the applicability of the Fourth Amendment to
noncitizens. For Fourth Amendment rights to attach, the alien must show ‘substantial connections’ with the United
States.”); United States v. Portillo-Muñoz, 643 F.3d 437, 440 (5th Cir. 2011).
89 See, e.g., United States v. Barona, 56 F.3d 1087, 1094 (9th Cir. 1995) (reasoning that “the people” for purposes of
Fourth Amendment protection includes citizens at home and abroad and lawful resident aliens within U.S. borders, but
declining to decide on whether a resident alien is entitled to constitutional protections once he or she steps outside of
U.S. territory).
90 Agency for Int’l Dev. v. All. for Open Soc’y Int’l, Inc., 140 S. Ct. 2082, 2086 (2020).
91 Compare Perez Cruz v. Barr, 926 F.3d 1128, 1145 (9th Cir. 2019) (considering Fourth Amendment challenge to the
detention of an unlawfully present alien who had resided in the United States for many years); Martinez-Aguero v.
Gonzalez, 459 F.3d 618, 625 (5th Cir. 2006) (ruling that alien present within the United States had “developed
substantial connections” for purposes of bringing a Fourth Amendment challenge because she had regularly and
lawfully visited the country on prior occasions); with Castro v. Cabrera, 742 F.3d 595, 600–01 (5th Cir. 2014) (holding
that “excludable” aliens detained at the border could not bring a Fourth Amendment challenge to their detention by
immigration authorities); United States v. Gutierrez-Casada, 553 F. Supp. 2d 1259, 1272 (D. Kan. 2008) (“[T]he court
is examining the Fourth Amendment rights of a previously deported, aggravated felonious illegal alien who chose to
reenter the United States knowing that the sovereign country, by due process of law, had recently ordered him to leave
and stay out of the country. Simply put, such persons are not entitled to the same Fourth Amendment protections as are
ordinary citizens.”). See generally Moore, supra note 88, at 834–42 (discussing uncertainty regarding the Fourth
Amendment’s application to unlawfully present aliens in the years following Verdugo-Urquidez).
92 See Moore, supra note 88, at 834–35, 841–42 (discussing the relationship between Verdugo-Urquidez and other
cases where alienage did not appear to be a deciding factor in the Court’s Fourth Amendment analysis).
93 Verdugo-Urquidez, 494 U.S. at 272.
94 Id.
95 Id.
96 See, e.g., Perez Cruz, 926 F.3d at 1145 (holding that suspicionless detention of unlawfully present alien, who had
resided in the United States for more than a decade violated the Fourth Amendment); Yanez-Marquez v. Lynch, 789
F.3d 434, 445 (4th Cir. 2015) (considering Fourth Amendment claim raised by alien in removal proceedings); Cotzojay
v. Holder, 725 F.3d 172, 181 (2d Cir. 2013) (“[I]t is uncontroversial that the Fourth Amendment applies to aliens and
citizens alike.”); Martinez Carcamo v. Holder, 713 F.3d 916, 921 (8th Cir. 2013) (“We have observed that the Fourth
Amendment . . . applies as much to illegal aliens inside this country as it does to citizens.”); Martinez-Aguero, 459 F.3d
at 625 (observing in an excessive force case brought against a Border Patrol agent by a Mexican national with an
expired visa, and who had previously made monthly trips to the United States, that although “[t]here may be cases in
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receive protection under the Fourth Amendment because they lack the sufficient connections with
this country to be part of a “national community.”97 One district court, for example, rejected a
criminal defendant’s Fourth Amendment challenge to a search and seizure at the U.S.-Canada
border because, citing Verdugo-Urquidez, the defendant had not established a “significant
voluntary connection with the United States” to entitle him to Fourth Amendment protections.98
And some district courts, when applying Verdugo-Urquidez’s substantial connections test, have
held that previously deported felons are not entitled to Fourth Amendment protections because
their presence in the United States is prohibited by law.99
In short, whether aliens located within the interior of the United States who lack lawful
immigration status must satisfy the substantial connections test or a less stringent standard to
invoke Fourth Amendment protections remains unresolved by the courts.100 While many courts
have recognized that Fourth Amendment protections may apply to at least some unlawfully
present aliens, the circumstances of the aliens’ presence in the United States, including the nature
and length of their stay in the country, may be relevant.
There is some uncertainty regarding the application of the Fourth Amendment to nonresident
aliens seeking initial entry into the United States. Under Verdugo-Urquidez, such aliens arguably
lack Fourth Amendment protections because they lack substantial connections to the United
States. And courts have long held that aliens seeking to enter the United States have less robust
constitutional protections because they are deemed to be outside the country.101 But some courts
which an alien’s connection with the United States is so tenuous that he cannot reasonably expect the protection of its
constitutional guarantees; the nature and duration of [the Mexican national’s] contacts with the United States, however,
are sufficient to confer Fourth Amendment rights”); see also Moore, supra note 88, at 834–35 (“Given the prior
discussion of aliens’ Fifth and Sixth Amendment rights, it is perhaps not surprising that, generally speaking, aliens, just
as citizens, are entitled to the Fourth Amendment’s protections and to the exclusion, in domestic criminal proceedings,
of evidence obtained in violation of the Fourth Amendment. The Supreme Court implicitly endorsed this proposition in
1973 in Almeida-Sanchez v. United States, where the Court held that the warrantless search and seizure of a Mexican
citizen legally present in the United States violated the Fourth Amendment. In fact, the Almeida-Sanchez Court did not
even consider the impact of alienage on the analysis; instead, Justice Stewart, writing for the plurality, focused on
whether the search was properly encompassed within the administrative border-search exception.”).
97 See, e.g., United States v. Portillo-Muñoz, 643 F.3d 437, 440 (5th Cir. 2011) (“[N]either this court nor the Supreme
Court has held that the Fourth Amendment extends to a native and citizen of another nation who entered and remained
in the United States illegally.”); Gutierrez-Casada, 553 F. Supp. 2d at 1272 (holding that a previously deported
criminal alien who had unlawfully reentered the United States did not receive Fourth Amendment protections); United
States v. Esparza-Mendoza, 265 F. Supp. 2d 1254, 1271–73 (D. Utah 2003) (same); United States v. Ullah, No. 04-CR30A(F), 2005 WL 629487, at *30 (W.D.N.Y. Mar. 17, 2005) (“The record in the instant case, however, is devoid of
any evidence demonstrating that Ullah, an alien, had lawfully entered and resided in this country for a sufficient period
to trigger the application of Fourth or Fifth Amendment protections to the challenged border inspections to which he
was subjected.”).
98 Ullah, 2005 WL 629487, at *29.
99 Gutierrez-Casada, 553 F. Supp. 2d at 1272 (holding that, in light of Verdugo-Urquidez, a previously deported,
felonious, unlawfully present alien was not entitled to Fourth Amendment protections); Esparza-Mendoza, 265 F.
Supp. 2d at 1271 (holding that “previously deported alien felons, such as [defendant], are not covered by the Fourth
Amendment”).
100 See Mary Holper, The Unreasonable Seizures of Shadow Deportations, 86 U. CIN. L. REV. 923, 950 (2018) (“A
question that has gained increasing relevance since 1990, when the Court decided United States v. Verdugo-Urquidez,
is whether undocumented noncitizens are part of ‘the people’ protected by the Fourth Amendment.”); D. Carolina
Nuñez, Inside the Border, Outside the Law: Undocumented Immigrants and the Fourth Amendment, 85 S. CAL. L. REV.
85, 108 (2011) (noting that “there is no consensus on which classes of undocumented immigrants are outside the Fourth
Amendment’s ambit”).
101 See Zadvydas v. Davis, 533 U.S. 678, 693 (2001) (“It is well established that certain constitutional protections
available to persons inside the United States are unavailable to aliens outside of our geographic borders.”); Landon v.
Plasencia, 459 U.S. 21, 32 (1982) (“This Court has long held that an alien seeking initial admission to the United States
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have ruled that these constitutional limitations pertain only to challenges to procedures arising in
the context of immigration, and do not foreclose Fourth Amendment claims that implicate certain
fundamental rights, including when raised by nonresident aliens at the border.102
Searches
As discussed earlier, the Fourth Amendment protects against unreasonable searches and seizures.
Searches potentially affronting the Fourth Amendment tend to fall into two categories: (1)
searches of premises and other effects; and (2) searches of the person. A search of an area where
there is a reasonable expectation of privacy generally implicates the Fourth Amendment. Whether
a search has occurred is often determined by a two-part test set forth in Justice Harlan’s
concurring opinion to the Supreme Court’s decision in Katz v. United States: “first, that a person
have exhibited an actual (subjective) expectation of privacy and, second, that the expectation be
one that society is prepared to recognize as ‘reasonable.’”103 A search may also occur on a
trespass theory, that is, where the government obtains information by physically intruding on a
constitutionally protected area, such as a home.104
The Fourth Amendment also protects against unreasonable searches of the person.105 The
Supreme Court has found that intrusions on the body—whether by, for example, an external pat
requests a privilege and has no constitutional rights regarding his application, for the power to admit or exclude aliens
is a sovereign prerogative.”); Shaughnessy v. United States ex rel. Mezei, 345 U.S. 206, 212 (1953) (declaring that “an
alien on the threshold of initial entry stands on a different footing” than those who have “passed through our gates” for
purposes of receiving due process protections); Alvarez-Garcia v. Ashcroft, 378 F.3d 1094, 1097 (9th Cir. 2004)
(“Aliens ‘standing on the threshold of entry’ are ‘not entitled to the constitutional protections provided to those within
the territorial jurisdiction of the United States.’ ”) (quoting Ma v. Ashcroft, 257 F.3d 1095, 1107 (9th Cir.2001)). Cf.
DHS v. Thuraissigiam, 140 S. Ct. 1959, 1982–83 (2020) (An alien arriving at a U.S. port of entry, whether at a land
border or an international airport, is a “treated for due process purposes as if stopped at the border” despite being on
U.S. soil; this principle also extends to the treatment of an alien apprehended 25 yards from the border following his
unlawful entry.).
102 See Castro v. Cabrera, 742 F.3d 595, 600 (5th Cir. 2014) (“Therefore, if these detainees are excludable aliens
stopped before entry into the United States and their claims arise in the context of immigration, the entry fiction applies
and there is no violation of the Fourth Amendment. If, however, they were subject to wanton or malicious infliction of
pain or gross physical abuse, the doctrine does not apply, and we consider whether Cabrera was entitled to qualified
immunity.”); Martinez-Aguero v. Gonzalez, 459 F.3d 618, 623 (5th Cir. 2006) (holding that alien detained near the
border could be considered within the United States for purposes of asserting a Fourth Amendment claim because she
sought to challenge an officer’s use of excessive force outside the context of her immigration detention); Kwai Fun
Wong v. INS, 373 F.3d 952, 971 (9th Cir. 2004) (“The entry fiction thus appears determinative of the procedural rights
of aliens with respect to their applications for admission. The entry doctrine has not, however, been applied, by the
Supreme Court or by this court, to deny all constitutional rights to non-admitted aliens.”) (emphasis in original);
Tungwarara v. United States, 400 F. Supp. 2d. 1213, 1220 (N.D. Cal. 2005) (holding that the Fourth Amendment
requires “some level of suspicion” to conduct strip searches of non-admitted aliens because “intrusive searches of the
person implicate important dignity and privacy interests,” and “[t]hese interests are fundamental to all human beings,
not just admitted aliens and citizens”) (citing United States v. Flores-Montano, 541 U.S. 149, 152 (2004)).
103 Katz v. United States, 389 U.S. 347, 361 (1967) (Harlan, J., concurring) (ruling that the bugging of a phone booth
violated Katz’s Fourth Amendment right to be free from unreasonable search).
104 United States v. Jones, 565 U.S. 400, 406–07 (2012) (holding that the attachment of a GPS tracking device to a
vehicle and tracking of the vehicle’s movements was a search under the Fourth Amendment).
105 U.S. CONST. amend. IV (providing that “[t]he right of the people to be secure in their persons . . . against
unreasonable searches and seizures . . . shall not be violated”).
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down of a person106 or a surgical procedure to remove a bullet allegedly stemming from an
attempted robbery107—constitute searches for purposes of the Fourth Amendment.108
Once a search subject to Fourth Amendment scrutiny has occurred, a determination must be made
on whether it is “reasonable.”109 Reasonableness depends on the context. The Court has explained
that “the reasonableness standard ‘is judged by balancing its intrusion on the individual’s Fourth
Amendment interests against its promotion of legitimate governmental interests.’”110
Seizures
The Fourth Amendment also protects against unreasonable seizures of persons or property by law
enforcement. A seizure of property subject to Fourth Amendment scrutiny occurs when
governmental action meaningfully interferes with the suspect’s possessory interests.111 Such items
are typically stolen property and other “fruits” of criminal conduct, instrumentalities used in
committing a crime, contraband, and items that may constitute evidence of the commission of a
crime or of someone’s guilt.112 In most cases there must be probable cause to effect a seizure.113
The Fourth Amendment guards against seizures of the person.114 A person has been seized if, in
view of all the circumstances surrounding the incident, that person has an objective reason to
believe that he or she is not free to leave.115 As the Supreme Court has explained, an arrest—“the
quintessential ‘seizure of a person’”116—“requires either physical force ... or, where that is
absent, submission to the assertion of authority.”117 The Court has also held that the use of
physical force to apprehend a person evading arrest (e.g., shooting a fleeing suspect) constitutes a
seizure, even if the person does not submit and is not subdued.118
Other forms of detention, such as field detentions for investigation, may also be subject to Fourth
Amendment scrutiny.119 Courts generally conclude that if an individual is approached by an
106 See, e.g., Terry v. Ohio, 392 U.S. 1, 25 (1968) (reasoning that a search incident to an arrest and a limited search for
weapons on the person can justify a “relatively extensive exploration of a person”).
107 Winston v. Lee, 470 U.S. 753 (1985).
108 See Schmerber v. California, 384 U.S. 757, 768 (1966).
109 Vernonia Sch. Dist. 47J v. Acton, 515 U.S. 646, 653 (1995).
110 Id. at 652–53.
111 United States v. Jacobsen, 466 U.S. 109, 113 (1984).
112 Warden, Md. Penitentiary v. Hayden, 387 U.S. 294 (1967) (ruling that the Fourth Amendment permitted the seizure
of evidence “which would aid in apprehending and convicting criminals”); see also FED. R. CRIM. P. 41(c) (authorizing
issuance of a warrant to seize “evidence of a crime”; “contraband, fruits of crime, or other items illegally possessed”;
“property designed for use, intended for use, or used in committing a crime”; or “a person to be arrested or a person
who is unlawfully restrained”).
113 See Arizona v. Hicks, 480 U.S. 321, 326–27 (1987) (holding seizure in plain view must be supported by probable
cause).
114 U.S. CONST. amend. IV.
115 Michigan v. Chesternut, 486 U.S. 567, 573 (1988); see also United States v. Mendenhall, 446 U.S. 544, 553–54
(1980) (“We adhere to the view that a person is ‘seized’ only when, by means of physical force or a show of authority,
his freedom of movement is restrained.”).
116 California v. Hodari D., 499 U.S. 621, 624 (1991).
117 Id. at 626 (rejecting argument that an arrest “effected by the slightest application of physical force, despite the
arrestee’s escape” constitutes a seizure).
118 Torres v. Madrid, -- S. Ct. --, No. 19-292, 2021 WL 1132514, *7 (Mar. 25, 2021). See also Tennessee v. Garner,
471 U.S. 1, 7 (1985).
119 See, e.g., Terry v. Ohio, 392 U.S. 1, 4–6 (1968). In the seminal stop-and-frisk case, Terry v. Ohio, an officer
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officer and asked questions without the use of force, the individual is only “seized” if a
reasonable person would not feel free to disregard the police and walk away.120 An example of a
common “seizure” is the stopping of an automobile and its passengers, even if the stop is brief
and limited in scope.121
Once there has been a “seizure,” the Fourth Amendment requires an appraisal of whether that
seizure was a reasonable “invasion of a citizen’s personal security.”122
Standards of Suspicion: Probable Cause and Reasonable Suspicion
Typically, a government officer must have probable cause before he or she may make an arrest,
conduct a search, or obtain a warrant.123 The probable cause standard stems from the Fourth
Amendment’s requirement that “no Warrants shall issue, but upon probable cause.”124 This
requirement “protects citizens from rash and unreasonable interferences with privacy and from
unfounded charges of crime, while giving fair leeway for enforcing the law in the community’s
protection.”125 The Supreme Court has recognized that probable cause is a concept that is
imprecise, fluid, and dependent on the context of the search or seizure.126 Generally, there must be
an objectively reasonable basis for believing (1) a crime was committed (for an arrest)127 or (2)
evidence of the crime is present in the place to be searched (for a search).128 Mere suspicion is not
enough to satisfy this standard, but probable cause requires less than evidence which would
justify a conviction.129
observed that multiple persons were “hover[ing] about a street corner for an extended period of time,” were not waiting
for anyone or anything to happen, paced along an identical route, and regularly conferred. Id. Suspecting the
individuals of criminal activity, the officer approached the individuals to investigate. Id. at 7. The Court held that a
brief investigatory stop and search constituted a seizure and search subject to the reasonableness requirement of the
Fourth Amendment, even though the brief detention fell short of an arrest. Id. at 16.
120 Mendenhall, 446 U.S. at 553–54.
121 Delaware v. Prouse, 440 U.S. 648, 654 (1979) (explaining that the “permissibility of a particular law-enforcement
practice is judged by balancing its intrusion on the individual’s Fourth Amendment interests against its promotion of
legitimate governmental interests”); see also Mich. Dep’t. of State Police v. Sitz, 496 U.S. 444, 450 (1990) (holding
that a seizure subject to the constraints of the Fourth Amendment occurs when a vehicle is stopped at a temporary
sobriety checkpoint conducted by police).
122 Terry, 392 U.S. at 19.
123 See, e.g., Kentucky v. King, 563 U.S. 452, 459 (2011) (“[A] warrant may not be issued unless probable cause is
properly established[.]”); Brigham City, Utah v. Stuart, 547 U.S. 398, 402 (2006) (explaining exigent circumstance
search exception to the warrant requirement requires probable cause); Maryland v. Pringle, 540 U.S. 366, 370 (2003)
(requiring probable cause for warrantless arrest in a public place for a felony).
124 U.S. CONST. amend. IV (emphasis added).
125 Pringle, 540 U.S. at 370 (quoting Brinegar v. United States, 338 U.S. 160, 176 (1949)) (internal quotation marks
omitted)).
126 See Illinois v. Gates, 462 U.S. 213, 232 (1983) (“Perhaps the central teaching of our decisions bearing on the
probable cause standard is that it is a ‘practical, nontechnical conception.’ Brinegar v. United States, 338 U.S. 160
(1949) . . . [P]robable cause is a fluid concept—turning on the assessment of the probabilities in particular factual
contexts—not readily, or even usefully, reduced to a neat set of legal rules.”).
127 Pringle, 540 U.S. at 371 (“To determine whether an officer had probable cause for an arrest, the court examines the
events leading up to the arrest, and then decides whether these historical facts, viewed from the standpoint of an
objectively reasonable police officer, amount to probable cause.”).
128 See Gates, 462 U.S. at 230–31 (applying totality of circumstances approach).
129 Dunaway v. New York, 442 U.S. 200, 212 (1979); Wong Sun v. United States, 371 U.S. 471, 479 (1963) (citation
omitted) (“It is basic that an arrest with or without a warrant must stand upon firmer ground than mere suspicion,
though the arresting officer need not have in hand evidence which would suffice to convict.”).
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Although probable cause is generally required, some warrantless searches and seizures may be
based on “reasonable suspicion”—a less demanding standard—depending on the “totality of the
circumstances” surrounding the search or seizure.130 For instance, Fourth Amendment
jurisprudence allows for brief investigative stops when a law enforcement officer has “a
particularized and objective basis for suspecting the particular person of criminal activity.”131
Although a mere “hunch” does not create reasonable suspicion,132 the level of suspicion the
standard requires is “considerably less than proof of wrongdoing by a preponderance of the
evidence,” and “obviously less” than is necessary for probable cause.”133
Warrantless Searches and Seizures
To satisfy the Fourth Amendment’s reasonableness requirement, searches and seizures typically
require a government official to obtain a warrant based on probable cause.134 Searches and
seizures conducted without a warrant are presumptively unreasonable.135 But there are situations
in which a warrantless search may be reasonable under the Fourth Amendment including, as
discussed below, searches at international borders.
Searches at International Borders
Fourth Amendment jurisprudence recognizes searches and seizures at international borders as
exceptional cases for Fourth Amendment purposes.136 Under what is known as the border search
exception, searches performed at international borders do not generally require a warrant,
probable cause, or reasonable suspicion.137 This exception to the warrant and probable cause
requirements applies to outgoing as well as incoming travelers.138 The Supreme Court has stated
that searches at the border “are reasonable simply by virtue of the fact that they occur at the
border.”139 Citing a lower expectation of privacy at the border, the Court has articulated that “[t]he
Fourth Amendment balance between the interests of the Government and the privacy right of the
130 See Alabama v. White, 496 U.S. 325, 330–31 (1990).
131 Naverette v. California, 572 U.S. 393, 396 (2014).
132 Terry v. Ohio, 392 U.S. 1, 27 (1968).
133 Navarrete, 572 U.S. at 397 (quoting United States v. Sokolow, 490 U.S. 1, 7 (1989)).
134 See, e.g., Skinner v. Railway Labor Execs.’ Ass’n., 489 U.S. 602, 621–22 (1989).
135 See Horton v. California, 496 U.S. 128, 133 (1990). “Where a search is undertaken by law enforcement officials to
discover evidence of criminal wrongdoing, [the Supreme] Court has said that reasonableness generally requires the
obtaining of a judicial warrant.” Veronia Sch. Dist. 47J v. Acton, 515 U.S. 646, 653 (1995).
136 United States v. Ramsey, 431 U.S. 606, 617–19 (1977).
137 Id.
138 See United States v. Seljan, 547 F.3d 993, 999 (9th Cir. 2008) (noting that “searches at the international border of
both inbound and outbound persons or property” are subject to the border search doctrine); United States v. Odutayo,
406 F.3d 386, 392 (5th Cir. 2005) (“[W]e join our sister circuits in holding that the border search exception applies for
all outgoing searches at the border.”); United States v. Boumelhem, 339 F.3d 414, 420 (6th Cir. 2003)
(“Notwithstanding Boumelhem’s arguments, the border search exception applies to the search of the outgoing cargo
container here.”); United States v. Oriakhi, 57 F.3d 1290, 1297 (4th Cir. 1995) (“[W]e join the several other circuit
courts which have held that the Ramsey border search exception extends to all routine searches at the nation’s borders,
irrespective of whether persons or effects are entering or exiting from the country.”); United States v. Ezeiruaku, 936
F.2d 136, 143 (3d Cir. 1991) (holding that “the traditional rationale for the border search exception applies as well in
the outgoing border search context.”); see also D.E. v. Doe I, 834 F.3d 723, 727 (6th Cir. 2016) (border search of
motorist’s vehicle was lawful under the border search exception, even though the motorist claimed to have arrived at
the international border inadvertently and intended to turn around).
139 Ramsey, 431 U.S. at 616.
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individual is also struck much more favorably to the Government at the border.”140 That said, not
all searches at the border are per se reasonable under the Fourth Amendment. Some border
searches conducted in a particularly offensive manner—such as a body cavity search—may still
be limited by the Fourth Amendment.141 Simply stated, the reasonableness of a border search
depends on the circumstances of the search itself.142
The border search exception does not necessarily apply to each and every encounter between law
enforcement and persons at or near an international border. For example, as will be discussed
later, courts have held that “roving patrol” stops of vehicles near the border to question the
vehicle’s occupants must be justified by reasonable suspicion of unlawful activity.143 Rather, the
border search exception applies to searches occurring in the context of a border crossing, such as
when an individual arrives at a U.S. port of entry.
The Border and Its Functional Equivalent
Searches may potentially take place along any segment of the United States’ international border.
Government officials may perform searches at or near the land borders shared with Mexico and
Canada.144 Stops and searches may also be conducted at the “functional equivalent” of the
border.145 Because people can enter the country at points other than along the border, courts have
concluded that stops and searches conducted at the first point at which an entrant may practically
be detained to be the functional equivalent of the border.146 This includes an airport where an
international flight lands147 or the port where a ship docks after traveling from a foreign port.148
For instance, lower courts have determined that a pat-down of a passenger on a jetway departing
on an international flight took place at the functional equivalent of the border149 and the search of
a passenger arriving from a nonstop international flight at the Chicago O’Hare airport occurred at
140 United States v. Montoya de Hernandez, 473 U.S. 531, 539–40 n.4 (1985).
141 See id; see also United States v. Irving, 452 F.3d 110, 123 (2d Cir. 2006) (explaining that reasonable suspicion
would be required for a more invasive search); United States v. Whitted, 541 F.3d 480, 485–86 (3d Cir. 2008)
(contrasting “routine” “patdowns, frisks, luggage searches, and automobile searches” with “nonroutine” “body cavity
searches, strip searches, and x-ray examinations” that require reasonable suspicion).
142 See Montoya de Hernandez, 473 U.S. at 538 (noting that the Fourth Amendment’s balance of reasonableness is
qualitatively different at the international border than in the interior).
143 See, e.g., United States v. Brignoni-Ponce, 422 U.S. 873, 884 (1975) (requiring reasonable suspicion for roving
patrol stops near the border)
144 See, e.g., United States v. Chase, 503 F.2d 571 (9th Cir. 1974) (Mexico); United States v. Mastberg, 503 F.2d 465
(9th Cir. 1974) (Canada).
145 Almeida-Sanchez v. United States, 413 U.S. 266, 272–73 (1973).
146 See, e.g., United States v. Cardenas, 9 F.3d 1139, 1147 (5th Cir. 1993); United States v. Beras, 183 F.3d 22, 26 (1st
Cir. 1999). See also United States v. Bareno–Burgos, 739 F. Supp. 772, 778 (E.D.N.Y. 1990) (“Case law reflects that
the functional equivalent of the border need bear no particular time or space relationship to the actual border.”).
147 See, e.g., United States v. Yang, 286 F.3d 940, 944 (7th Cir. 2002) (explaining “even though Chicago is not an
international border, searches at customs at O’Hare are permissible under the functional equivalent doctrine.”); Beras,
183 F.3d at 26; United States v. Johnson, 991 F.2d 1287, 1290 (7th Cir. 1993) (search of passenger arriving on nonstop
international at O’Hare International Airport was at the functional equivalent to an international border). In other
words, passengers and cargo arriving on an international flight may be subject to an inspection, but passengers arriving
on a domestic flight are not subject to an inspection.
148 See, e.g., United States v. Prince, 491 F.2d 655 (5th Cir. 1974); United States v. LaFroscia, 485 F.2d 457 (2d Cir.
1973); Cardenas, 9 F.3d at 1147; United States v. Victoria-Peguero, 920 F.2d 77, 80 (1st Cir. 1990) (explaining that a
warrantless search at the functional equivalent of the sea border was consistent with Fourth Amendment).
149 Beras, 183 F.3d at 26.
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the functional equivalent.150 Additionally, post offices receiving international airmail are the
functional equivalent of the border.151 Importantly, these locations are treated as the functional
equivalent of the border only to the extent that a search at that location pertains to persons or
items believed to be traveling to or from the United States.152
Searches and Seizures: Routine and Nonroutine
Under the border search exception, federal officers may generally conduct warrantless searches of
persons and things upon their entry into the United States, without needing reasonable suspicion
or probable cause of wrongdoing.153 But, depending on the level of intrusion, some searches
performed at the international border may require reasonable suspicion.154 When determining
whether a search is reasonable, Fourth Amendment jurisprudence generally categorizes searches
at the border into two categories: routine searches and nonroutine searches—with the latter
requiring a level of particularized suspicion of illegal activity.
Routine Searches and Seizures
The Supreme Court has discussed what constitutes a nonroutine search;155 it has not explicitly
defined the scope of searches that may be categorized as routine. According to lower courts,
routine searches generally include searches of automobiles, baggage, and other goods entering the
country.156 Additionally, an individual seeking to enter the country may be required to submit to a
search of his or her outer clothing,157 which may include an examination of the contents of a
purse, wallet, or pockets and a canine sniff.158 While this is ongoing, the individual may be
subject to a brief detention.159
150 Johnson, 991 F.2d at 1290.
151 United States v. Ramsey, 431 U.S. 606, 620 (1977) (rejecting any distinction between items mailed to the United
States and items carried into the United States).
152 See, e.g., United States v. Jackson, 825 F.2d 853, 876 (5th Cir. 1987) (en banc). In that case, the Fifth Circuit held
that a highway checkpoint 14 miles from the international border did not constitute the functional equivalent of the
border because it did not contain traffic “‘international’ in character.” Id. The court explained that the equivalent of the
border must not “intercept no more than a negligible number of domestic travelers.” Id. at 860.
153 See United States v. Montoya de Hernandez, 473 U.S. 531, 538 (1985); United States v. Lincoln, 494 F.2d 833, 837
(9th Cir. 1974); United States v. King, 485 F.2d 353, 358 (10th Cir. 1973); United States v. Beck, 483 F.2d 203, 207
(3d Cir. 1973); United States v. Stornini, 443 F.2d 833, 835 (1st Cir. 1971).
154 See Montoya de Hernandez, 473 U.S. at 537–38 (discussing Fourth amendment reasonableness requirement at the
border).
155 See generally id.
156 See, e.g., Angulo v. Brown, 978 F.3d 942, 949 (5th Cir. 2020) (“The Government does not need to show any level
of suspicion to thoroughly search an entrant’s vehicle at the border.”); United States v. Sandoval Vargas, 854 F.2d 1132
(9th Cir. 1988) (car); United States v. Flores, 594 F.2d 438 (5th Cir. 1979) (car); United States v. Lafroscia, 485 F.2d
457 (2d Cir. 1973) (car); United States v. Gonzalez, 483 F.2d 223 (2d Cir. 1973) (baggage); United States v. Stornini,
443 F.2d 833 (1st Cir. 1971) (baggage).
157 See, e.g., United States v. Braks, 842 F.2d 509 (1st Cir. 1988) (holding that requiring a female suspect to lift her
dress somewhat in a private room with a female inspector present was part of routine border search); United States v.
Nieves, 609 F.2d 642 (2d Cir. 1979) (holding that requiring a person to remove a shoe is part of routine border search
but drilling into shoes is not routine border search); United States v. Flores, 477 F.2d 608 (1st Cir. 1973).
158 See, e.g., United States v. Kelly, 302 F.3d 291, 294–95 (5th Cir. 2002) (canine sniff was routine border search,
reasoning a canine sniff “is no more intrusive than a frisk or a pat-down, both of which clearly qualify as routine border
searches”).
159 See, e.g., Angulo, 978 F.3d at 950 (ruling that an hour of questioning was within the government’s power and that
“removing Angulo from his vehicle and handcuffing him were only necessary because Angulo refused to exit the
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As explained by the Seventh Circuit, a routine search is one that does “not pose a serious invasion
of privacy” and “embarrass or offend the average traveler.”160 For instance, the removal and
examination of a suitcase’s contents, including through the use of an x-ray, by a customs
inspector constitutes a routine search.161 Similarly, the Fifth Circuit has defined a “routine” search
as “one that does not ‘seriously invade a traveler’s privacy,’” thereby requiring a reviewing court
to evaluate “‘the invasion of the privacy and dignity of the individual.’”162 The Fifth Circuit has
classified “ordinary pat-downs or frisks, removal of outer garments or shoes, and emptying of
pockets, wallets, or purses” as routine.163 Likewise, the Second Circuit has described routine
searches as to include searches of outer clothing, luggage, a purse, wallet, pockets, or shoes,
“which, unlike strip searches, do not substantially infringe on a traveler’s privacy rights.”164
In United States v. Braks, the First Circuit set forth several factors relevant to assessing whether a
search was routine.165 In that case, a customs official had searched a foreign national by taking
her into a private room and conducting a search of her garments by gesturing without physical
contact, resulting in the foreign national raising her garment.166 In determining the degree of
invasiveness of any particular search, the First Circuit set forth several factors to consider:
(i) whether the search results in the exposure of intimate body parts or requires the suspect
to disrobe; (ii) whether physical contact between Customs officials and the suspect occurs
during the search; (iii) whether force is used to effect the search; (iv) whether the type of
search exposes the suspect to pain or danger; (v) the overall manner in which the search is
conducted; and (vi) whether the suspect’s reasonable expectations of privacy, if any, are
abrogated by the search.167
The court concluded that the search was a justified and routine search on the rationale that the
foreign national did not have to actually remove her clothing or expose herself; no physical
contact or force was used; the search did not include any pain or danger; and the search was
conducted in a private room by a female customs official.168 The First Circuit explained that this
list of factors is not exhaustive, stressing that “each case must turn upon its particularized
facts.”169
vehicle voluntarily on his own”); United States v. Nava, 363 F.3d 942 (9th Cir. 2004) (individual was not subject to an
“arrest” when officer asked him to exit truck, handcuffed him, escorted him to security office to be patted down, and
was required to wait while officer inspected pickup truck).
160 United States v. Johnson, 991 F.2d 1287, 1291 (7th Cir. 1993) (conducting a “scratch test,” “flex test,” and “weight
test” on baggage).
161 Id. at 1293–94 (during routine inspection, customs official developed reasonable suspicion that she was smuggling
contraband into the country).
162 Kelly, 302 F.3d at 294 (quoting United States v. Cardenas, 9 F.3d 1139, 1148 n.3 (5th Cir 1993); United States v.
Sandler, 644 F.2d 1163, 1167 (5th Cir. 1981)).
163 Kelly, 302 F.3d at 294.
164 Tabbaa v. Chertoff, 509 F.3d 89, 98 (2d Cir. 2007).
165 See United States v. Braks, 842 F.2d 509, 511–12 (1st Cir. 1988).
166 Id. at 510–11.
167 Id. at 511–12.
168 Id. at 512–13.
169 Id. at 513.
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Nonroutine Searches and Seizures Requiring Reasonable Suspicion
A court may determine a nonroutine search has occurred once a search goes beyond a limited
intrusion. Nonroutine border searches—such as prolonged detentions, strip searches, body cavity
searches, or involuntary x-ray searches—require reasonable suspicion.170
Inspections of Persons. The 1985 Supreme Court decision United States v. Montoya de
Hernandez offers insight into what searches and detentions at the border may be classified as
nonroutine searches and therefore require reasonable suspicion.171 In that case, an airline traveler
arrived at the Los Angeles International Airport from Bogotá, Colombia.172 Upon questioning by
customs inspectors, the traveler revealed that she did not speak English, did not have family or
other connections in the United States, was planning to purchase goods for her husband’s store in
Bogotá, possessed $5,000 in cash, and had no hotel reservations.173 Based on this information, her
frequent traveling to the United States, and firm abdomen, the customs inspectors suspected she
was smuggling narcotics through her alimentary canal and detained her until her bowels passed—
taking around 16 hours.174 In a challenge to criminal convictions for unlawful possession and
importation of cocaine, the Supreme Court ruled that her detention did not violate the Fourth
Amendment because—even though it went beyond the scope of a routine customs inspection—it
was based on reasonable suspicion that she was smuggling contraband.175
This decision articulated a few important principles when it comes to the constitutionality of
prolonged detentions and nonroutine searches. Montoya de Hernandez seemingly mandates that
searches beyond a routine search and detention at the border must be supported by reasonable
suspicion.176 Furthermore, Montoya de Hernandez suggests that detentions, even extended delays
of 16 or more hours, may be constitutionally permissible if the detention “was reasonably related
in scope to the circumstances which justified it initially.”177 There, the Court held that the
detention lasting 16 or more hours was reasonable under the circumstances because the time of
detention corresponded to the time it took for the defendant’s bowels to pass and therefore was
“necessary to either verify or dispel the suspicion was not unreasonable.”178
There are no bright-line rules on when a routine search or detention transforms into nonroutine. In
another Supreme Court decision, United States v. Flores-Montano, the Supreme Court held that a
one-hour delay incident to a border search did not render the search nonroutine and therefore did
not require suspicion, reasoning that “delays of one to two hours at international borders are to be
expected.”179 The Fourth Amendment does not “shield[] entrants from inconvenience or delay at
170 United States v. Montoya de Hernandez, 473 U.S. 531, 541 n.4 (1985). See, e.g., United States v. Garcia-Garcia, 319
F.3d 726, 730 (5th Cir. 2003) (alert by drug sniffing dog constituted reasonably suspicion supporting detention of bus
for time reasonably necessary to investigate the cause of the alert).
171 473 U.S. 531 (1985).
172 Id. at 532–33.
173 Id. at 533.
174 Id. at 534.
175 Id. at 541.
176 See id. at 541–42.
177 Montoya de Hernandez, 473 U.S. at 542.
178 Id. at 544.
179 United States v. Flores-Montano, 541 U.S. 149, 155 n.3 (2004).
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the international border.”180 Rather, the focus is on whether the detention was reasonable in light
of the circumstances.181
A lower court’s opinion suggests that even searches and detentions lasting several hours may not
require reasonable suspicion. In Tabbaa v. Chertoff, the Second Circuit considered whether a
search and a detention lasting four to six hours at the U.S.-Canada border violated the plaintiffs’
Fourth Amendment rights.182 The U.S. citizen plaintiffs claimed the combined effect of the
measures used—intrusive questioning, photographing, and fingerprinting—was not routine and
therefore required some level of suspicion.183 The court held that the combined effect of routine
elements did not transform the stop into a nonroutine search because each of the individual
elements themselves were routine.184 The court also rejected the plaintiffs’ contention that the
threat of detention until they complied transformed the search into a nonroutine search, reasoning
that “border crossers cannot, by their own non-compliance, turn an otherwise routine search into a
nonroutine one.”185 Lastly, the Second Circuit held that the detention was routine because
“common sense and ordinary human experience suggest that it may take up to six hours for CBP
to complete the various steps at issue here, including vehicle searches, questioning, and identity
verification, all of which [were] already found to be routine.”186
Searches of Vehicles. As discussed previously, government officials may search automobiles
seeking entry to the United States without reasonable suspicion.187 But in United States v. FloresMontano, the Supreme Court considered whether a more intrusive search of a car—involving the
removal, disassembly, and reassembly of a fuel tank—constituted a search requiring suspicion of
illegal activity.188 Noting the government’s “paramount interest in protecting the border,” the
Court held that the government’s authority to conduct suspicionless border inspections includes
the authority to remove, disassemble, and reassemble a fuel tank.189 But the Flores-Montano court
declined to address whether and under what circumstances a search of a vehicle at the
international border would “be deemed unreasonable because of the particularly offensive manner
in which it is carried out.”190
Still, there is no hard-and-fast rule for when a search of a vehicle becomes so intrusive as to
require reasonable suspicion. Before Flores-Montano, several circuit courts held that the
government must have reasonable suspicion before drilling into an individual’s property in search
180 Id.
181 Montoya de Hernandez, 473 U.S. at 542.
182 Tabbaa v. Chertoff, 509 F.3d 89, 95 (2d Cir. 2007) (involving U.S. citizen plaintiffs who were returning from an
Islamic conference in Canada).
183 Id. at 98.
184 Id. at 99.
185 Id. at 100.
186 Id. (internal quotation marks omitted).
187 See Carroll v. United States, 267 U.S. 132, 154 (1925).
188 United States v. Flores-Montano, 541 U.S. 149, 151 (2004).
189 Id. at 155.
190 Id. at 155 n.2 (internal citation and quotation marks omitted).
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of contraband.191 The Supreme Court distinguished Flores-Montano from these circuit decisions
because the fuel tank was reassembled, unlike “potentially destructive drilling.”192
Several Ninth Circuit decisions post Flores-Montano support the notion that destruction to a
vehicle or its components might not require suspicion of illegal activity (other circuit courts have
not weighed in since Flores-Montano193). In United States v. Cortez-Rocha, the Ninth Circuit held
that cutting open a spare tire did not require reasonable suspicion.194 Although the court
acknowledged the damage to the tire, the court observed that the destruction of the spare tire did
not interfere with the operation of the vehicle or hinder the traveler’s immediate ability to
continue his travels using that automobile.195 In another decision, the Ninth Circuit held that the
drilling of a single small-diameter hole in a pickup truck did not require reasonable suspicion
because it did not significantly damage the truck.196 But in United States v. Guzman-Padilla, the
Ninth Circuit held that the deflating of tires required reasonable suspicion because the vehicle
was rendered inoperable.197 Guzman-Padilla clarified the factors for determining whether a
search of a vehicle required reasonable suspicion: “(1) Did the search damage the vehicle in a
manner that affected the vehicle’s safety or operability, and (2) Was the search conducted in a
particularly offensive manner.”198 In other words, damage to a vehicle does not transform a border
search into a nonroutine search; the severity of that damage to the vehicle’s functionality may be
a key consideration in assessing whether reasonable suspicion is required.
Other Exceptions to the Fourth Amendment’s Warrant Requirement
That May Be Relevant to Encounters Near the Border
In addition to the border search exception, courts have recognized other circumstances where a
warrantless search may be permitted under the Fourth Amendment. Some of these exceptions
may be relevant to law enforcement encounters at or near the international border or its functional
equivalent:
Search Incident to Lawful Arrest. A government officer who lawfully arrests an
individual may conduct a warrantless search of the arrestee’s person and the area
“within his immediate control” from which the suspect might gain possession of
191 See, e.g., United States v. Rivas, 157 F.3d 365, 367 (5th Cir. 1998) (holding drilling into the body of a trailer
required reasonable suspicion); Untied States v. Robles, 45 F.3d 1 (1st Cir. 1995) (drilling into machine part required
reasonable suspicion); United States v. Carreon, 872 F.2d 1436 (10th Cir. 1989).
192 Flores-Montano, 541 U.S. at 155 n.2.
193 But see United States v. De Jesus-Viera, 655 F.3d 52 (1st Cir. 2011). In that case, the First Circuit held that a
drilling by CBP into a vehicle did not violate the Fourth Amendment. Id. at 58. The trial court had concluded that the
drilling was a routine border search. Id. at 57–58. But on appeal, the First Circuit declined to weigh in on whether the
search was a routine search or a nonroutine search because, even if it was nonroutine, there was reasonable suspicion to
justify the drilling. Id. at 58.
194 United States v. Cortez-Rocha, 394 F.3d 1115, 1119–20 (9th Cir. 2006) (concluding that the search and disabling of
a vehicle’s spare tire “does not in any way hinder the operation of the vehicle or impede the traveler’s immediate ability
to continue his travels using the vehicle”).
195 Id. at 1120.
196 United States v. Chaudhry, 424 F.3d 1051, 1053 (9th Cir. 2005).
197 United States v. Guzman-Padilla, 573 F.3d 865, 879 (9th Cir. 2009).
198 Id.; see also United States v. Hernandez, 424 F.3d 1056 (9th Cir. 2005) (holding no reasonable suspicion as required
where the government removed the interior door panels with a screwdriver so that doors could be put back together
without damage, causing no significant damage nor did it undermine the safety of the vehicle).
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a weapon or destructible evidence.199 This exception stems from interests in
officer safety and evidence preservation following an arrest.200
Stop and Frisk. A law enforcement officer may detain an individual briefly upon
reasonable suspicion of criminal activity, and conduct a frisk when the officer is
“justified in believing that the individual . . . is armed and presently dangerous to
the officer or to others.”201 A frisk is limited to a search for weapons202 and
cannot be justified by a need to prevent the destruction of evidence (but in the
event a search for weapons leads to the discovery of contraband, that finding may
permit the officer to seize the item under the plain view exception discussed
below, and the discovery of contraband may lead to a criminal arrest).203 If a
search exceeds these bounds, it must be justified by a warrant or another
exception to the warrant requirement.204
Emergency Aid, Exigent Circumstances, or Hot Pursuit. A warrantless search
may be permissible if the “exigencies of the situation make the needs of law
enforcement so compelling that a warrantless search is objectively reasonable
under the Fourth Amendment.”205 Examples of exigent circumstances include
providing emergency assistance in a residence or engaging in a “hot pursuit” of a
fleeing suspect.206
Plain View. Government officers may seize an item of an incriminating nature in
“plain view” without a warrant.207 Examples of when such a seizure may be
permissible include when an officer comes across some other article of an
incriminating nature while performing a search of an area for certain objects
pursuant to a lawful warrant; when an officer finds an incriminating article while
the officer is engaged in a hot pursuit; or when an officer comes across an
incriminating object while conducting a search incident to a lawful arrest.208
Searches in Open Fields. The Fourth Amendment does not protect against
searches in “open fields,” such as rural farmland, even if the intrusion onto the
lands is a common-law trespass.209 Open fields are distinct from a property
199 Davis v. United States, 564 U.S. 229, 232 (2011).
200 Arizona v. Gant, 556 U.S. 332, 338 (2009).
201 Adams v. Williams, 407 U.S. 143, 145 (1972) (citing Terry v. Ohio, 392 U.S. 1, 22 (1968)).
202 Terry, 392 U.S. at 29; see also Michigan v. Long, 463 U.S. 1032 (1983) (holding that protective search of a
vehicle’s passenger compartment during a lawful stop did not affront the Fourth Amendment where the circumstances
were such that a person would reasonably believe that his safety or the safety of others was at risk); Ybarra v. Illinois,
444 U.S. 85, 93–94 (1979) (“Nothing in Terry can be understood to allow a generalized ‘cursory search for weapons’
or indeed, any search whatever for anything but weapons.”); Adams, 407 U.S. at 146–47 (1972) (explaining a search of
weapons must be “limited in scope to this protective purpose”).
203 See Minnesota v. Dickerson, 508 U.S. 366, 374–75 (1993) (explaining that a search is no longer valid and its fruits
will be suppressed if a Terry protective search goes beyond what is necessary to determine whether the suspect is
armed).
204 See id. at 374–75.
205 Missouri v. McNeely, 569 U.S. 141, 148–49 (2013) (quoting Kentucky v. King, 563 U.S. 452, 460 (2011)).
206 Id. at 148–49.
207 Horton v. California, 496 U.S. 128, 134 (1990).
208 Coolidge v. New Hampshire, 403 U.S. 443, 465–66 (1971).
209 Hester v. United States, 265 U.S. 57, 58 (1924). An example of the open fields exception is found in Oliver v.
United States, 466 U.S. 170 (1984), in which police officers entered a farm in rural Kentucky without a search warrant.
They investigated the property and came upon a marijuana field surrounded on all sides by woods, fences, and
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owner’s curtilage, “the area to which extends the intimate activity associated with
the ‘sanctity of a man’s home and the privacies of life,’” which fall under the
scope of the Fourth Amendment’s protections.210
Search Following Consent. A search to which an individual consents satisfies
Fourth Amendment requirements.211
Roadblock-type Stops Unrelated to Border Crossings. As discussed later,
checkpoints may be established at or near the border to detect unlawful border
crossings.212 Government officers may also briefly stop and question individuals
without any suspicion of criminal activity at checkpoints to advance certain law
enforcement objectives.213 The Supreme Court has held that a sobriety
checkpoint was reasonable under the Fourth Amendment, given the state’s
interest in preventing driving under the influence of alcohol, the extent the
checkpoint advanced that interest, and the minimal intrusion on individuals who
were briefly stopped.214 In another decision, the Court held that a highway
checkpoint program with a primary purpose of discovering illegal narcotics
affronted the Fourth Amendment.215 In short, whether a checkpoint survives
Fourth Amendment scrutiny depends on a balancing of the competing interests at
stake and the effectiveness of the program.216
Warrantless Arrests
Although the Fourth Amendment generally requires law enforcement officers to obtain an arrest
warrant, an officer may lawfully arrest persons if the officer observes the arrestee committing an
offense or if the officer has probable cause to believe the arrestee has committed any felony.217
Indeed, INA Section 287(a) authorizes immigration officers to arrest aliens without a warrant in
certain circumstances—those in the act of unlawfully entering the country; those who an
immigration officer has “reason to believe” are unlawfully present in the United States and are
likely to escape before an arrest warrant can be obtained; and those reasonably suspected to have
committed a felony.218
embankment and hidden from public view. Id. at 173.
210 Id. at 180 (quoting Boyd v. United States, 116 U.S. 616, 630 (1886)).
211 Katz v. United States, 389 U.S. 347, 358 n.22 (1967).
212 See infra “Fixed Immigration Checkpoints.”
213 See City of Indianapolis v. Edmond, 531 U.S. 32, 37–38 (2000).
214 Michigan v. Sitz, 496 U.S. 444, 455 (1990).
215 Edmond, 531 U.S. at 48. The Court distinguished the narcotics checkpoint from the sobriety checkpoint in Sitz,
reasoning that the narcotics checkpoint program was indistinguishable from the general interest in crime control. Id.
at 41–42.
216 Id. at 47.
217 Michigan v. DeFillippo, 443 U.S. 31, 36 (1979) (holding that arrest by officer who observed conduct violating a
presumptively valid ordinance was not in violation of the Fourth Amendment).
218 See 8 U.S.C. § 1357(a) (conferring arrest authority to officers designated under prescribed regulations).
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Government Searches Beyond the Border and Its
Functional Equivalent
The Fourth Amendment’s warrant requirement generally does not apply to routine searches and
seizures at the border or its functional equivalent of persons arriving in the United States. The
government may conduct routine searches in these circumstances without probable cause or any
suspicion of unlawful activity. But the government’s border enforcement activities are not
confined to the physical border or its functional equivalent. For example, the government may
conduct searches and seizures in areas beyond the border to prevent unlawfully present aliens
who have evaded detection from traveling further into the interior of the United States, or to
prevent the importation of drugs and other contraband.219
In some circumstances, searches away from the border may be conducted without a judicial
warrant. For instance, courts have recognized that “extended border searches” can be conducted
of persons believed to have recently crossed the border and to be engaged in illegal activity.
Additionally, government officers may conduct other types of searches beyond the border that do
not necessarily require a physical entry into the United States. These searches include the
boarding of vessels along coastal waterways, “roving patrols” near the border, fixed immigration
checkpoints, and transportation checks.
Given their physical distance from the actual border, some of these searches may require at least
heightened suspicion or probable cause of unlawful activity to withstand Fourth Amendment
scrutiny.220
A table comparing the different types of warrantless searches and seizures that may occur at the
border and surrounding areas, including searches at the border or its functional equivalent,
immigration checkpoints, roving patrols, extended border searches, and the boarding of vessels,
can be found in Table A-3.
Extended Border Searches
While the doctrine has not been endorsed or applied by the Supreme Court, several lower courts
have concluded that the government may conduct warrantless, “extended border searches” of
certain individuals beyond the border or its functional equivalent.221 Courts have reasoned that
immigration and customs officials may not learn of criminal activity until after a vehicle or
219 See United States v. Villamonte-Marquez, 462 U.S. 579, 593 (1983) (recognizing the government’s interest in
patrolling inland or coastal waters “where the need to deter or apprehend smugglers is great”); United States v.
Martinez-Fuerte, 428 U.S. 543, 552 (1976) (“Although the Border Patrol maintains personnel, electronic equipment,
and fences along portions of the border, it remains relatively easy for individuals to enter the United States without
detection.”) (citing United States v. Brignoni-Ponce, 422 U.S. 873, 879 (1975)); Almeida-Sanchez v. United States,
413 U.S. 266, 268 (1973) (noting that the Border Patrol conducts inland surveillance activities “all in the asserted
interest of detecting the illegal importation of aliens”).
220 See, e.g., United States v. Singh, 415 F.3d 288, 294 (2d Cir. 2005) (“Border Patrol operations along inland routes—
not at the border or its functional equivalent—including permanent checkpoints, temporary checkpoints, and roving
patrols are held to a higher standard.”).
221 See United States v. Cardenas, 9 F.3d 1139, 1148 (5th Cir. 1993) (noting that “the border search doctrine has been
extended to allow government officials to conduct a warrantless search and seizure beyond the border or its functional
equivalent”); United States v. Caicedo-Guarnizo, 723 F.2d 1420, 1422 (9th Cir. 1984) (“The ‘extended border’ doctrine
is an expansion of this rule; it permits the Government to conduct border searches some time after the border has been
crossed.”).
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person has physically crossed the border, and that the government has a strong interest in
preventing importation of narcotics and contraband.222 Thus, unlike searches at a border’s
functional equivalent (e.g., an international airport), an extended border search occurs at some
point after an individual could have been first stopped from entering the United States.223
Yet because extended border searches occur after a person has entered the United States (and
potentially has already been inspected at the border), they intrude more upon a searched
individual’s privacy expectations than searches at the border or its functional equivalent, where
the government’s authority is more pronounced.224 Thus, lower courts have adopted a three-part
test to determine whether an extended border search is reasonable under the Fourth
Amendment.225 Under this test, an extended border search must meet these criteria:
1. “Reasonable certainty” (or a “high degree of probability”) that a border crossing
has occurred;
2. “reasonable certainty” that no change in the condition of the person or vehicle
being searched has occurred since the border crossing, and that any contraband
found was present when the person or vehicle crossed the border; and
3. reasonable suspicion of criminal activity.226
222 See Cardenas, 9 F.3d at 1149 (“The major impetus behind the extended border search doctrine is ‘the government
interest in stopping drug traffic.’ ”) (quoting WILLIAM E. RINGEL, SEARCHES AND SEIZURES, ARRESTS AND CONFESSIONS,
§ 15.3 (Supp. 1993)); United States v. Alfonso, 759 F.2d 728, 734 (9th Cir. 1985) (“Customs agents may learn or
realize the significance of suspicious circumstances only after a vehicle or person has crossed the border.”) (citing
Jones v. United States, 326 F.2d 124 (9th Cir. 1963)); United States v. Bilir, 592 F.2d 735, 740 (4th Cir. 1979) (“The
many difficulties that attend the attempt to intercept contraband and to apprehend increasingly mobile and sophisticated
smugglers at the very borders of the country have of course given birth to the doctrine.”). Additionally, “the agents may
delay a search in a reasonable effort to sweep in associates of suspected smugglers.” Alfonso, 759 F.2d at 734 (citing
United States v. Espericueta-Reyes, 631 F.2d 616, 619–20 (9th Cir. 1980)).
223 United States v. Guzman-Padilla, 573 F.3d 865, 878 (9th Cir. 2009) (citing United States v. Niver, 689 F.2d 520,
526 (5th Cir. 1982)); see also United States v. Stewart, 729 F.3d 517, 526 (6th Cir. 2013) (“Courts typically apply the
doctrine in situations where customs agents returned custody of an item, or where customs agents never took custody of
the item at the border, but conducted a subsequent search of that item after the custodian and the items had cleared
customs.”); United States v. Glaziou, 402 F.2d 8, 12–13 (2d Cir. 1969) (describing the “border area” as being “elastic”
and extending to the area “in the immediate vicinity of any entry point”). Courts have distinguished extended border
searches from functional border searches, particularly in criminal cases where the defendant argued that the
government search should have been subject to heightened scrutiny because it occurred away from the border. See, e.g.,
Stewart, 729 F.3d at 525–26 (concluding that defendant was not subject to an extended border search, even though one
of his laptop computers was examined at a CBP field office 20 miles from the airport, because his computer had not
been “cleared” for entry, and thus there was “no attenuation” between his border crossing and the search of his
computer); United States v. Cotterman, 709 F.3d 952, 961–62 (9th Cir. 2013) (holding that extended border search
doctrine did not apply to forensic examination of laptop computer at laboratory 170 miles from the border because the
computer “never cleared customs so entry was never effected”).
224 See Cotterman, 709 F.3d at 961 (“The key feature of an extended border search is that an individual can be assumed
to have cleared the border and thus regained an expectation of privacy in accompanying belongings.”); United States v.
Yang, 286 F.3d 940, 946 (7th Cir. 2002) (“The constitutional concern of extending the border in this manner is that it
potentially permits searches with less than probable cause at significant distances from our national borders.”); United
States v. Cardenas, 9 F.3d 1139, 1148 (5th Cir. 1993) (“An extended border search, however, entails a greater intrusion
on an entrant's legitimate expectations of privacy than does a search conducted at the border or its functional
equivalent.”).
225 Yang, 286 F.3d at 946 (“Because an extended border search entails greater intrusion on an entrant's legitimate
expectations of privacy than does a search conducted at the border or its functional equivalent, courts have instituted
the three-part test to ensure that the search is reasonable.”) (citing Cardenas, 9 F.3d at 1148).
226 See Stewart, 729 F.3d at 525; Guzman-Padilla, 573 F.3d at 878–79; Yang, 286 F.3d at 945; Cardenas, 9 F.3d
at 1148; United States v. Caminos, 770 F.2d 361, 364 (3d Cir. 1985); Alfonso, 759 F.2d at 734; United States v. Garcia,
672 F.2d 1349, 1364 (11th Cir. 1982). To determine whether there was “reasonable certainty” of a border crossing (or
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Courts have applied the three-pronged test when considering Fourth Amendment challenges to
extended border searches. For instance, in one case, the Ninth Circuit held that Border Patrol
agents lawfully searched a vehicle spotted near the U.S.-Mexico border.227 The court found there
was reasonable certainty that the driver had just crossed the border because his vehicle was
encountered in a remote area less than two miles from the border, accessible only through a valley
originating in Mexico.228 The Ninth Circuit concluded that the agents had reasonable suspicion
for the search because the vehicle was in a known smuggling route, had Mexican license plates,
drove erratically, and contained a black tarp covering in the back.229
In another case, the Fifth Circuit ruled that agents lawfully searched a woman encountered in El
Paso, Texas, just a block from a pedestrian border crossing.230 The court determined there was
reasonable certainty that the woman had just crossed the border because a checkpoint search of
her companion suggested they had been traveling together.231 The Fifth Circuit also found there
was reasonable certainty that there was no changed condition of the woman or her belongings
given the brief time and distance that had passed since she crossed the border and was
searched.232 The court further ruled there was reasonable suspicion to search the woman because
evidence seized from her companion indicated they were trafficking narcotics.233
Courts have upheld extended border searches on many other occasions.234 In a few cases, though,
courts have concluded that the challenged search did not meet the extended border search criteria.
“reasonable certainty” that the condition of the person or vehicle remained unchanged since the crossing), courts
consider the “totality of the surrounding circumstances,” such as the time and distance from the original entry and the
manner and extent of any surveillance. Guzman-Padilla, 573 F.3d at 879 (quoting Alexander v. United States, 362 F.2d
379, 382 (9th Cir. 1966)). The “reasonable certainty” standard is higher than probable cause, but does not require proof
beyond a reasonable doubt. Id. at 880 (citing United States v. Corral-Villavicencio, 753 F.2d 785, 788 (9th Cir. 1985));
United States v. Espinoza-Seanez, 862 F.2d 526, 531 (5th Cir. 1988) (citing United States v. Driscoll, 632 F.2d 737,
739 (9th Cir. 1980)). Instead, “the totality of the facts and circumstances within the officers’ knowledge and of which
they have reasonably trustworthy information [must] be sufficient in the light of their experience to warrant a firm
belief that a border crossing has occurred.” United States v. Tilton, 534 F.2d 1363, 1366–67 (9th Cir. 1976) (alteration
added). Thus, the officers are not required to show an absolute certainty of a border crossing. Guzman-Padilla, 573
F.3d at 880.
227 Guzman-Padilla, 573 F.3d at 880–82.
228 Id. at 881.
229 Id. at 882.
230 Cardenas, 9 F.3d at 1151–53.
231 Id. at 1151. In concluding there was a reasonable certainty that the woman had recently crossed the border, the court
observed that evidence of a border crossing “may be inferred from circumstantial evidence.” Id. at 1150 (internal
citation omitted).
232 Id. at 1152–53. The court held that the Border Patrol does not have to show there was “continuous surveillance” to
establish a reasonable certainty of an individual’s unchanged condition from the time of the border crossing, noting that
the court had previously upheld extended border searches where individuals were unobserved for up to 30 minutes or
close to an hour. Id. at 1152.
233 Id. at 1153. See also United States v. Alfonso, 759 F.2d 728, 735 (9th Cir. 1985) (“The fact that some search
occurred at the time of the initial border crossing simply does not prevent later searches from coming under the rules of
border searches.”) (citing United States v. Caicedo-Guarnizo, 723 F.2d 1420, 1422–23 (9th Cir. 1984)).
234 See, e.g., United States v. Villasenor, 608 F.3d 467, 472–74 (9th Cir. 2010) (ruling that search of individual’s
vehicle was proper because ICE agents had surveilled vehicle after it crossed the border, and they had received a tip
that the vehicle was being used for a drug trafficking operation); United States v. Yang, 286 F.3d 940, 947–49 (7th Cir.
2002) (upholding search of individual who had already passed through customs where it was undisputed that he had
just arrived at Chicago O’Hare International Airport; it was reasonably certain there was no change in the condition of
his luggage because it had been out of his control for a significant period of time; and there was reasonable suspicion
that he was trafficking narcotics); United States v. Espinoza-Seanez, 862 F.2d 526, 531–32 (5th Cir. 1988) (concluding
that search of automobile was reasonable because agents had noticed tracks leading to and from the border in an area
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For instance, the Ninth Circuit held that Border Patrol agents unlawfully searched a truck
suspected of carrying narcotics because they did not first see the truck until it was three miles
north of the border in the middle of a busy border town, and the Border Patrol agents could not
have been reasonably certain the truck or its cargo had recently crossed the border.235 Although
the agents learned afterward that the truck had been in the United States for only 90 minutes
before being spotted, “[t]he 90-minute gap in surveillance was enough to change the contents of
the truck, and therefore, the customs agents could not be reasonably certain any contraband found
in the truck had crossed the border.”236 Thus, the legality of an extended border search turns on
the specific facts and circumstances in each case.237
Boarding and Inspection of Vessels Within Interior and Coastal
Waterways
Government searches beyond the border are not strictly limited to land searches and seizures. The
federal government may also inspect vessels encountered within interior and coastal waterways.
Under federal statutes, customs officers may board vessels found “at any place in the United
States” or the “customs waters” (i.e., within 12 nautical miles from the coastline), to examine
documents, conduct inspections, and search the vessel and its cargo for contraband and other
potential federal customs violations.238 Additionally, Coast Guard officers (who also have
customs enforcement powers) have authority to board certain vessels in U.S. waters and the high
seas to examine documentation and conduct inspections and searches for potential violations of
federal law.239 For purposes of the Fourth Amendment, courts have treated the stopping of
waterborne vessels near the border differently than the stopping of automobiles on land, given a
vessel’s access to the open sea and the impracticability of establishing maritime checkpoints.240
where the vehicle had previously been seen, the agents had followed the vehicle both by helicopter and on the ground,
and there was reasonable suspicion of criminal activity); United States v. Alfonso, 759 F.2d 728, 736–37 (9th Cir.
1985) (holding that search of Colombian ship in Los Angeles harbor was permissible because it occurred within a dayand-a-half after its arrival in U.S. waters and after an initial cursory search); United States v. Garcia, 672 F.2d 1349,
1367 (11th Cir. 1982) (upholding search of plane that had been under continuous surveillance after crossing the border
where there was reasonable suspicion that it was involved in drug smuggling); United States v. Bilir, 592 F.2d 735, 741
(4th Cir. 1979) (holding that agents reasonably searched individual some seven hours after an observed border crossing,
where the search had been delayed to confirm developing suspicion that the individual was engaged in drug
smuggling).
235 United States v. Perez, 644 F.2d 1299, 1302 (9th Cir. 1981).
236 Id. The court determined, moreover, that “government agents will not be allowed to justify an extended border
search with information which was not available to the agents at the time of the search.” Id. (citing United States v.
Ramos, 473 F. Supp. 1109, 1111 (S.D. Fla. 1979)). Given the inapplicability of the extended border search doctrine, the
court determined that the government failed to show that there was probable cause or consent for the vehicle search. Id.
at 1302–03; see also Almeida-Sanchez v. United States, 413 U.S. 266, 273 (1973) (holding that Border Patrol agents on
“roving patrol” must have probable cause to search a vehicle).
237 The Supreme Court has not addressed the concept of extended border searches. But, as discussed in this report, the
Court has addressed other types of interior enforcement activities occurring near the border that—unlike extended
border searches—do not necessarily require the physical crossing of the border. See United States v. VillamonteMarquez, 462 U.S. 579 (1983); United States v. Martinez-Fuerte, 428 U.S. 543 (1976); United States v. Ortiz, 422 U.S.
891 (1975); United States v. Brignoni-Ponce, 422 U.S. 873 (1975); Almeida-Sanchez v. United States, 413 U.S. 266
(1973).
238 19 U.S.C. §§ 482(a), 1581(a).
239 14 U.S.C. § 522(a). The statute requires the vessel to be “subject to the jurisdiction, or to the operation of any law,
of the United States.” Id.
240 See United States v. Villamonte-Marquez, 462 U.S. 579, 589 (1983) (“But no reasonable claim can be made that
permanent checkpoints would be practical on waters such as these where vessels can move in any direction at any time
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Thus, courts have interpreted the Fourth Amendment as permitting government officials, acting
under lawful authority, to board vessels without a warrant, probable cause, or any suspicion of
unlawful activity, so long as the boarding is limited in nature. But some courts have held that
government officers may not conduct more intrusive searches of the vessel without particularized
suspicion of a crime.
United States v. Villamonte-Marquez
In United States v. Villamonte-Marquez, the Supreme Court considered whether the Fourth
Amendment limits the government’s authority under federal statutes to board and inspect vessels
in U.S. waters further into the interior of the United States.241 In that case, customs officials
boarded a sailboat 18 miles inland from the Gulf coast to inspect documents, and they discovered
marijuana inside the vessel.242 The owners of the sailboat argued that boarding their vessel
without reasonable suspicion violated the Fourth Amendment.243 The government argued that 19
U.S.C. § 1581 authorized the boarding without suspicion.244
The Court rejected the Fourth Amendment challenge, reasoning that, since 1790, Congress has
authorized the suspicionless boarding of vessels, “reflecting its view that such boardings are not
contrary to the Fourth Amendment.”245 Additionally, the Court reasoned, although the Court has
required reasonable suspicion for “roving patrol” stops of vehicles near the border,246 “[t]he
nature of waterborne commerce in waters providing ready access to the open sea” made the
boarding of vessels distinguishable.247 The Court observed that, unlike vehicle stops, there is no
practical alternative of stopping all vessels at permanent water checkpoints.248 The Court
concluded that the government’s interest in assuring compliance with vessel documentation
requirements, particularly in heavy drug trafficking areas, outweighed any “modest intrusion”
from boarding a vessel.249 The Court thus held that government officers may board vessels on
and need not follow established ‘avenues’ as automobiles must do. Customs officials do not have as a practical
alternative the option of spotting all vessels which might have come from the open sea and herding them into one or
more canals or straits in order to make fixed checkpoint stops.”); Cross v. Mokwa, 547 F.3d 890, 900 (8th Cir. 2008)
(“The Supreme Court expressly distinguished searches of such sea vessels from those of automobiles on land.”).
241 Villamonte-Marquez, 462 U.S. at 581 (“We are asked to decide whether the Fourth Amendment is offended when
Customs officials, acting pursuant to this statute and without any suspicion of wrongdoing, board for inspection of
documents a vessel that is located in waters providing ready access to the open sea.”).
242 Id. at 583.
243 Id. at 585.
244 Id.
245 Id. at 592. The Court described a 1790 statute authorizing the boarding of vessels as a “lineal ancestor” to 19 U.S.C.
§ 1581. Villamonte-Marquez, 462 U.S. at 584. According to the Court, “the enactment of this statute by the same
Congress that promulgated the constitutional amendments that ultimately became the Bill of Rights gives the statute an
impressive historical pedigree.” Id. at 585.
246 See United States v. Brignoni-Ponce, 422 U.S. 873, 884 (1975) (requiring reasonable suspicion for roving patrol
stops near the border); compare with United States v. Martinez-Fuerte, 428 U.S. 543, 562, 566 (1976) (holding that
fixed checkpoint stops near the border require no reasonable suspicion). For additional discussion about roving patrols
and immigration checkpoints in the interior of the United States, see infra “Roving Patrols” & “Fixed Immigration
Checkpoints.”
247 Villamonte-Marquez, 462 U.S. at 588–89.
248 Id. at 589. In addition, “[t]he system of prescribed outward markings used by States for vehicle registration is also
significantly different than the system of external markings on vessels, and the extent and type of documentation
required by federal law is a good deal more variable and more complex than are the state vehicle registration laws.” Id.
at 593.
249 Id. at 592. The Court described the routine customs inspections as “a brief detention where officials come on board,
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inland waters with ready access to the open sea for routine document checks without suspicion of
unlawful activity.250
Lower Courts’ Decisions on Boarding of Vessels
Lower courts have also recognized the government’s broad authority to board vessels and
conduct routine inspections without a warrant or any individualized suspicion.251 Courts have
held that, during the inspection, the officers may visit public areas of the vessel and observe
anything in plain view.252 But officers must have at least reasonable suspicion to conduct a more
intrusive search of the vessel, and probable cause for an exhaustive “stem to stern” search.253
While the government’s ability to conduct warrantless searches of vessels within interior or
coastal waterways is generally limited to routine safety and document inspections (unless there is
particularized suspicion of unlawful activity), the authority to board and search vessels crossing
the international border is less restrained.254 Lower courts have recognized that, if a vessel is
believed to have recently crossed the border into the United States, customs officials generally
visit public areas of the vessel, and inspect documents.” Id.
250 Id. at 593.
251 See, e.g., United States v. Albano, 722 F.2d 690, 695 (11th Cir. 1984) (“Customs officers may board a vessel in
Customs waters to check its documents even if the boarding serves merely as a pretext for the officers’ desire to look
for signs of contraband.”); United States v. Helms, 703 F.2d 759, 762–63 (4th Cir. 1983) (“Customs officers are, by
express statute, authorized to stop and board for a documentary examination any vessel within the ‘customs waters,’ . . .
with or without any suspicion of criminal activity.”); United States v. Watson, 678 F.2d 765, 771 (9th Cir. 1982)
(declaring that “the Coast Guard has plenary authority to stop vessels for document and safety inspections” without any
suspicion); United States v. Hilton, 619 F.2d 127, 131 (1st Cir. 1980) (“We believe the limited intrusion represented by
a document and safety inspection on the high seas, even in the absence of a warrant or suspicion of wrongdoing, is
reasonable under the fourth amendment.”); United States v. Freeman, 579 F.2d 942, 946 (5th Cir. 1978) (“The
reasonableness and constitutionality of brief stops of vessels in Customs waters by Customs agents for the purpose of
routine document and safety checks is beyond question.”).
252 See United States v. Cardona-Sandoval, 6 F.3d 15, 23 (1st Cir. 1993) (stating that the inspection “must be confined
to areas reasonably incident to the purpose of the inspection”); United States v. Humphrey, 759 F.2d 743, 746 (9th Cir.
1985) (concluding that routine Coast Guard inspection was limited to publicly exposed deck area and did not extend to
living quarters below deck); United States v. Herrera, 711 F.2d 1546, 1550 n.6 (11th Cir. 1983) (“At a minimum, it
allows Customs officers to view those non-private areas of the vessel which are in the plain view of a lawful boarding
party.”); United States v. Garcia, 598 F. Supp. 533, 537 (S.D. Fla. 1984) (“Once properly aboard a vessel, officers are
given a considerable opportunity to detect illegal activity. They may visit public areas of the boat and observe anything
in plain view.”).
253 See Cardona-Sandoval, 6 F.3d at 23 (stating that reasonable suspicion authorizes only a “limited intrusion” of
vessel); United States v. Roy, 869 F.2d 1427, 1430 (11th Cir. 1989) (“A full stem to stern search is permissible on
probable cause that a crime has been, or is being, committed.”); Herrera, 711 F.2d at 1550 (“We hold today that where
Customs officers have a reasonable suspicion that Customs violations exist, they may board a vessel to conduct a
limited ‘search’ of the non-private areas of the vessel.”); Hilton, 619 F.2d at 131 (“A more extensive search is
permissible only if there is consent or probable cause to believe a crime has been or is being committed.”); United
States v. Williams, 617 F.2d 1063, 1087 (5th Cir. 1980) (holding that the Fourth Amendment requires at least
reasonable suspicion to search a vessel); Garcia, 598 F. Supp. at 537 (“Once properly aboard a vessel, officers cannot
conduct an exhaustive search unless by the time their limited inspection is complete their suspicions have ripened into
probable cause.”).
254 See United States v. Alfonso, 759 F.2d 728, 734 (9th Cir. 1985) (“The rules of the ‘border search’ extend to
crossings of ocean boundaries as well as the land boundaries with Mexico and Canada.”); Blair, 665 F.2d at 505 (“The
requirements that the fourth amendment’s reasonableness standard imposes upon a vessel seizure vary greatly
according to that vessel’s geographic location.”).
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may stop and search the vessel beyond the scope of a routine document inspection with no
suspicion that a crime is afoot.255
Roving Patrols
The U.S. Border Patrol frequently conducts “roving patrols” near the border to enforce federal
immigration and drug laws.256 A roving patrol occurs when Border Patrol agents traverse certain
areas near the border and stop vehicles suspected of carrying unlawfully present aliens or illegal
narcotics, even if there is not necessarily an indication the vehicle had crossed the border.257
Unlike immigration checkpoints discussed later in this report—which occur at established points
on roads near the border and may require all drivers to stop for brief questioning258—roving
patrols do not occur at fixed locations and only target those suspected of engaging in unlawful
activity.259 Additionally, unlike extended border searches, roving patrols may stop vehicles
regardless of whether the vehicle and its occupants had crossed the border, and regardless of
whether the condition of the vehicle and its occupants had changed since a border crossing.
As discussed below, the Supreme Court and lower courts have addressed the constitutional
limitations on roving patrols, concluding that Border Patrol officers may randomly stop vehicles
near the border so long as they have reasonable suspicion that the occupants are engaged in
unlawful activity (e.g., smuggling aliens). But the officers may not search the vehicle in the
absence of probable cause or consent.
255 See United States v. Alfaro-Moncada, 607 F.3d 720, 732 (9th Cir. 2010) (holding that customs officers could search
living quarters inside foreign cargo ship docked at a port of entry without any suspicion); United States v. Pickett, 598
F.3d 231, 235 (5th Cir. 2010) (“Our precedent establishes that a border crossing occurs whenever a vessel crosses from
international waters into the United States, regardless of the defendant's departure point.”); United States v. Dobson,
781 F.2d 1374, 1376 (9th Cir. 1986) (“Customs officials may thus conduct a border search of any ship arriving in port
which is known to have sailed from international waters.”); Herrera, 711 F.2d at 1552 (“Our cases have clearly
distinguished between border searches which are reasonable because they occur at the border and limited Customs
searches in the maritime context which are reasonable if based on a reasonable suspicion of Customs violations.”);
United States v. Helms, 703 F.2d 759, 763 (4th Cir. 1983) (explaining that stopping and boarding a vessel in inland or
coastal waterways is deemed to occur at the border’s functional equivalent if the vessel had recently crossed the
border).
256 See Martinez-Fuerte, 428 U.S. at 552 (noting that “roving patrols are maintained to supplement the [immigration]
checkpoint system”). While such patrols normally take place in the vicinity of the border, there are some instances
when they have been conducted at more considerable distances. See United States v. Venzor-Castillo, 991 F.2d 634,
634–35, 639–40 (10th Cir. 1993) (holding that a Border Patrol stop of a vehicle some 235 miles from the border did not
occur within a reasonable distance permitted under statute).
257 See United States v. Ortiz, 422 U.S. 891, 894 (1975) (noting that roving patrols “often operate at night on seldomtraveled roads” and “look for criminal activity, both alien smuggling and contraband smuggling”).
258 See Martinez-Fuerte, 428 U.S. at 558–60 (describing the “regularized manner” of routine checkpoint stops).
259 See Moving the Line of Scrimmage: Re-Examining the Defense-In-Depth Strategy, Hearing Before the Subcomm. on
Border and Maritime Sec. of the H. Comm. on Homeland Sec., 114th Cong. (2016) (written testimony of U.S. Border
Patrol Chief Mark Morgan) (“Generally, Border Patrol agents employ two means to stop vehicles driven by smugglers
using side roads to circumvent a checkpoint: additional checkpoints and roving patrols. USBP may establish and
coordinate tactical checkpoints on circumvention routes, so as to ensure the effectiveness of checkpoints on main
thoroughfares. USBP may also conduct roving patrols, an acceptable and effective means to stop vehicles driven by
smugglers using side roads to circumvent an immigration checkpoint. Border Patrol agents on roving patrol may stop a
vehicle only if they have reasonable suspicion, based upon specific articulable facts and rational inferences from those
facts, that the vehicle contains individuals who may have illegally entered the United States.”).
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Almeida-Sanchez v. United States
In Almeida-Sanchez v. United States, the Supreme Court addressed the constitutionality of roving
patrols under the Fourth Amendment.260 In that case, the Border Patrol had stopped a motorist
some 25 air miles north of the U.S.-Mexico border and found marijuana inside his vehicle.261 The
motorist, who was convicted of illegally transporting marijuana, argued that the officers lacked
probable cause and that the search of his vehicle therefore violated the Fourth Amendment.262 In
response, the government argued that the vehicle search was permissible under INA Section
287(a)(3), which authorizes warrantless searches of vehicles and other conveyances within a
“reasonable distance” of the border.263
The Supreme Court held that the search of the vehicle violated the Fourth Amendment.264
Recognizing the federal government’s authority to conduct routine inspections and searches at the
border without a warrant or probable cause, the Court determined that roving patrol searches of
vehicles at points removed from the physical border or its functional equivalent “was of a wholly
different sort.”265 The Court reasoned that the government’s interests at the border are less potent
in the interior of the United States, where individuals have greater Fourth Amendment protections
against governmental intrusion.266 The Court concluded that such searches required either
probable cause or consent to the search.267
United States v. Brignoni-Ponce
The Almeida-Sanchez Court considered whether roving patrol searches, in which Border Patrol
agents search vehicles for evidence of illegal activity, were permissible under the Fourth
Amendment. In United States v. Brignoni-Ponce, the Court considered the constitutionality of
roving patrol stops, in which agents stop vehicles for the more limited purpose of questioning the
occupants about immigration status and any suspicious circumstances.268 In that case, Border
Patrol agents stopped a vehicle because the occupants appeared to be of Mexican descent.269
Upon questioning the driver and his two passengers, the agents learned they had entered the
260 Almeida-Sanchez v. United States, 413 U.S. 266, 269 (1973).
261 Id. at 267–68.
262 Id.
263 Id. at 268; see also 8 U.S.C. § 1357(a)(3) (authorizing immigration officers to engage in warrantless search of
vehicle “within a reasonable distance from any external boundary of the United States”); 8 C.F.R. § 287.1(a)(2)
(defining “reasonable distance” as “within 100 air miles from any external boundary of the United States or any shorter
distance which may be fixed by” the Border Patrol).
264 Almeida-Sanchez, 413 U.S. at 272–73.
265 Id. at 273.
266 Id. at 274–75.
267 Id. The Court observed that, although it had previously held that the government may stop and search an automobile
without a warrant, see, e.g., Carroll v. United States, 267 U.S. 132 (1925), that exception “does not declare a field day
for the police in searching automobiles.” Almeida-Sanchez, 413 U.S. at 269. “Automobile or no automobile, there must
be probable cause for the search.” Id. The Court also determined that, although it had previously ruled that the
government may conduct certain types of administrative inspections on less than probable cause, see Camara v.
Municipal Ct., 387 U.S. 523 (1967), United States v. Biswell, 406 U.S. 311 (1972), Colonnade Catering Corp. v.
United States, 397 U.S. 72 (1970), those decisions were inapposite because they still required the government inspector
to obtain a warrant before conducting the search; and they involved inspections of federally licensed and regulated
commercial enterprises. Almeida-Sanchez, 413 U.S. at 270–71.
268 United States v. Brignoni-Ponce, 422 U.S. 873, 874 (1975).
269 Id. at 875.
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United States unlawfully and arrested them.270 The driver, who was convicted of illegally
transporting aliens,271 argued that he was subject to an unlawful seizure.272 The government
argued that it had authority to conduct the stop without a warrant or any particularized suspicion
under the INA.273 The government further argued that preventing the unlawful entry of aliens into
the United Stat
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