<P> Searches conducted at the United States border or the equivalent of the border (such as an international airport) may be conducted without a warrant or probable cause subject to the border search exception . Most border searches may be conducted entirely at random, without any level of suspicion, pursuant to U.S. Customs and Border Protection plenary search authority . However, searches that intrude upon a traveler's personal dignity and privacy interests, such as strip and body cavity searches, must be supported by "reasonable suspicion ." The U.S. Courts of Appeals for the Fourth and Ninth circuits have ruled that information on a traveler's electronic materials, including personal files on a laptop computer, may be searched at random, without suspicion . </P> <P> The Supreme Court decision in United States v. U.S. District Court (1972) left open the possibility for a foreign intelligence surveillance exception to the warrant clause . Three United States Courts of Appeals have recognized a foreign intelligence surveillance exception to the warrant clause, but tied it to certain requirements . The exception to the Fourth Amendment was formally recognized by the United States Foreign Intelligence Surveillance Court of Review in its 2008 In re Directives decision . The lower court held that, "a foreign intelligence exception to the Fourth Amendment's warrant requirement exists when surveillance is conducted to obtain foreign intelligence for national security purposes and is directed against foreign powers or agents of foreign powers reasonably believed to be located outside the United States ." Despite the foregoing citation the Fourth Amendment prohibitions against unreasonable searches and seizures nonetheless apply to the contents of all communications, whatever the means, because, "a person's private communications are akin to personal papers ." To protect the telecommunication carriers cooperating with the US government from legal action, the Congress passed a bill updating the Foreign Intelligence Surveillance Act of 1978 to permit this type of surveillance . </P> <P> In New Jersey v. T.L.O. (1985), the Supreme Court ruled that searches in public schools do not require warrants, as long as the searching officers have reasonable grounds for believing that the search will result in the finding of evidence of illegal activity . However, in Safford Unified School District v. Redding (2009), the Court ruled that school officials violated the Fourth Amendment when they strip searched a 13 - year - old girl based only on a student claiming to have received drugs from that student . Similarly, in Samson v. California (2006), the Court ruled that government offices may be searched for evidence of work - related misconduct by government employees on similar grounds . Searches of prison cells are subject to no restraints relating to reasonableness or probable cause . </P> <P> One way courts enforce the Fourth Amendment is through the use of the exclusionary rule . The rule provides that evidence obtained through a violation of the Fourth Amendment is generally not admissible by the prosecution during the defendant's criminal trial . The Court stated in Elkins v. United States (1960) that the rule's function "is to deter--to compel respect for the constitutional guaranty in the only effectively available way--by removing the incentive to disregard it ." </P>

There are two parts to the fourth amendment the reasonableness clause and the