Border search exception
The border search exception is a doctrine of United States criminal law that allows searches and seizures at international borders and their functional equivalent without a warrant or probable cause.
This doctrine is not actually an exception to the Fourth Amendment, but rather to the Amendment's requirement for a warrant (or probable cause). Balanced against the sovereign's interests at the border are the Fourth Amendment rights of entrants. Not only is the expectation of privacy less at the border than in the interior   the Fourth Amendment balance between the interests of the Government and the privacy right of the individual is also struck much more favorably to the Government at the border. This balance at international borders means that routine searches are "reasonable" there, and therefore do not violate the Fourth Amendment's proscription against "unreasonable searches and seizures".
Border searches more invasive than "routine" require some suspicion. See the section below.
Despite federal law allowing certain federal agents to conduct suspicionless search and seizures within 100 miles of the border, the Supreme Court has clearly and repeatedly confirmed that the border search exception applies only at international borders and their functional equivalent (such as international airports).
The United States Customs and Border Protection (CBP), ICE-HSI Special Agents, and Coast Guard officers (E4 grade and above) who are all customs officers (those tasked with enforcing Title 19 of the United States Code) with the United States Department of Homeland Security, are permitted to search travelers and their belongings at the American border without probable cause or a warrant.  Pursuant to this authority, customs officers may generally stop and search the property of any traveler entering or exiting the United States at random, or even based largely on ethnic profiles.
Property searches 
At the border, customs officers are authorized to search all travelers' closed containers without any level of suspicion. This authority extends to all physical containers, regardless of size or the possible presence of personal, confidential or embarrassing materials. Pursuant to this authority, Customs may also open and search incoming international mail.
Electronic materials 
Currently, the main area of contention concerning the border search exception is its application to the search of the electronic files and information contained in travelers' laptops and other electronic storage devices for illlegal materials including child pornography. Two notable decisions have been rendered with the respective intermediate appellate courts backing the United States Government's position that the search of electronic devices falls under the category of property searches and that the devices are functionally and qualitatively equivalent to other closed containers. According to this position, the Government asserts that it may open, login, and search through all the electronic information stored on traveler's electronic devices. The only federal appeals court to address this issue directly, the Ninth Circuit Court of Appeals, agreed with the government's position and held that "reasonable suspicion is not needed for customs officials to search a laptop or other electronic device at the international border."
Some have challenged the government's constitutional authority to search the contents of their laptops on two bases: (1) first, they claim that searches of the contents of their laptops violate their First Amendment freedom of expression; and (2) second, they claim that searches of the files on their electronic devices are unreasonable under the Fourth Amendment because they are a substantial intrusion into travelers' privacy and dignity interests.
The Fourth Circuit Court of Appeals, addressing a challenge to Customs' authority to search electronic files in United States v. Ickes, held that there is no First Amendment exception to the border search doctrine for expressive materials . The Court based its finding in part on the demands of protecting the nation from terrorist threats that may cross the American border in expressive materials. in its analysis, the Court stated:
The border search doctrine is justified by the longstanding right of the sovereign to protect itself. Particularly in today's world, national security interests may require uncovering terrorist communications, which are inherently “expressive.” Following Ickes's logic would create a sanctuary at the border for all expressive material-even for terrorist plans. This would undermine the compelling reasons that lie at the very heart of the border search doctrine."
Ickes did not directly address the required level of suspicion for laptop searches because customs officers in this case met the reasonable suspicion standard. However, the only court to address the Fourth Amendment protections of laptops at the national border held that customs may search any electronic device at the border without any level of suspicion. In United States v. Arnold, the Ninth Circuit Court of Appeals rejected a defendant's contention that search of travelers' files on a laptop computer intrude upon a person's dignity and privacy interests to the same degree as searches of a traveler's body. Instead, the court ruled that searches of electronic materials are legally equivalent to searches of property. As such, Customs' authority to search electronic materials at the border are limited in only two ways: (1) the search may not cause exceptional damage to the property; and (2) the search may not be conducted in "a particularly offensive manner." These restrictions are applicable to all border searches of property, at least under the jurisdiction of these courts. According to Arnold, the characteristics that make electronic storage devices unique, including vast storage capacity and the ability to track its user's habits, tastes, and preferences, are not legally significant. Additionally, the Ninth Circuit held that searching through personal electronic information in a laptop does not constitute an "offensive search."
Although the Supreme Court has not addressed the standard of suspicion necessary for a warrantless border search of electronic materials, the only jurisprudence thus far, guided by Ickes and Arnold, suggests that customs officers may search any electronic materials (including laptops, CDs, MP3 players, cellular phones, and digital cameras) randomly, without any suspicion, and without any first amendment restrictions.
One major impact of these cases is that commerce may be exceptionally impacted. Sensitive business information, academic materials for conferences, and other types of valuable information may be delayed by these practices. Some devices may be held for years, effectively making this a deprivation of property under the Fifth Amendment. Sensitive information that is withheld that long could lose all value. Many devices depreciate in value over time due to introduction of new devices, and this depreciation of the physical device could also be considered a taking.
Searches of travelers' bodies 
Although routine searches of the persons and effects of entrants are not subject to any requirement of reasonable suspicion, probable cause, or warrant, more invasive searches or seizures of a person's body require some suspicion.
The Supreme Court has held "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." (emphasis added) Characterized in terms of the Fourth Amendment, the Court was saying that such a detention ("seizure") was "reasonable", and therefore did not violate the Fourth Amendment. (The federal agents in this particular case did not X-ray ("search") her because she claimed she was pregnant. They instead decided to detain her long enough for ordinary bowel movements to evacuate the alimentary canal, despite her "heroic" efforts otherwise.)
The Supreme Court expressly did not rule what level of suspicion would be necessary for a strip, body-cavity, or involuntary x-ray search, though they did say that the only two standards for Fourth Amendment purposes short of a warrant were "reasonable suspicion" and "probable cause" (rejecting a "clear indication" standard).
In the border search context, reasonable suspicion means that the facts known to the customs officer at the time of the search, combined with the officer's reasonable inferences from those facts, provides the officer with a particularized and objective basis for suspecting that the search will reveal contraband. To form a basis for reasonable suspicion, a customs officer may rely on his training and prior experience, and may rely on entirely innocent factors, if the totality of the circumstances provide the officer with reasonable suspicion.
See also 
- "United States v. Ramsey, 431 US 606 (1977)". Retrieved 9 September 2012.
- Carroll v. United States
- Florida v. Royer
- Almeida-Sanchez v. United States, 413 US 266 - Supreme Court 1973
- § 287 (a) (3) of the Immigration and Nationality Act, 66 Stat. 233, , which simply provides for warrantless searches of automobiles and other conveyances "within a reasonable distance from any external boundary of the United States," as authorized by regulations to be promulgated by the Attorney General. The Attorney General's regulation, 8 CFR § 287.1, defines "reasonable distance" as "within 100 air miles from any external boundary of the United States."
- Although it has been claimed "These searches are therefore exempted from the Fourth Amendment warrant requirement" (emphasis added), federal law never supersedes the U.S. Constitution as interpreted by the U.S. Supreme Court. Such federal law is enforceable only to the extent that its application does not conflict with the U.S. Constitution.
- United States v. Montoya de Hernandez, 473 U.S. 531, 538 (1985) ("travelers may be stopped [and searched] at . . . the border without individualized suspicion even if the stop [or search] is based largely on ethnicity[.]") (citing United States v. Martinez-Fuerte, 428 U.S. 543, 562-563(1976))
- See Flores-Montano, 541 U.S. at 152-53; Montoya de Hernandez, 473 U.S. at 538.
- See 19 U.S.C. § 482; United States v. Ramsey, 431 U.S. 606 (1977)
- See Opening Brief of the United States of America 30-31, United States v. Arnold, appeal No. 06-50581 (9th Cir. June 13, 2007), 2007 WL 1407234 ("Computer devices are conceptually no different for Fourth Amendment purposes than other closed storage containers that are subject to suspicionless searches at the border.")
- United States v. Arnold, 2008 WL 1776525 at *4 (9th Cir. 2008). see The Ninth Circuit reversed the District Court's holding on April 21, 2008.
- United States v. Ickes, 393 F.3d 501, 504 (4th Cir. 2005)
- United States v. Arnold, 454 F. Supp. 2d 999, 1003-04 (N.D. Cal. 2006); rev'd 2008 WL 1776525 (9th Cir. 2008).
- Ickes, 393 F.3d at 506-07.
- Ickes, 393 F.3d at 506.
- Ickes, 393 F.3d at 506.
- United States v. Arnold, 2008 WL 1776525 (9th Cir. 2008).
- Arnold, 2008 WL 1776525 at *2-3.
- Arnold, 2008 WL 1776525 at *4-5.
- see United States v. Ross, 456 U.S. 798 (1982).
- Arnold, 2008 WL 1776525 at *5.
- United States v. Montoya de Hernandez, 473 US 531 - Supreme Court 1985
- The Montoya de Hernandez Court said, "It is also important to note what we do not hold. Because the issues are not presented today we suggest no view on what level of suspicion, if any, is required for nonroutine border searches such as strip, body-cavity, or involuntary x-ray searches. Both parties would have us decide the issue of whether aliens possess lesser Fourth Amendment rights at the border; that question was not raised in either court below and we do not consider it today."
- Montoya de Hernandez, 473 U.S. at 541.