Courts have found that the government has a strong interest in controlling and protecting U.S. borders. For this reason, they have created what is essentially an exception to the Fourth Amendment. This exception allows U.S. Customs and Border Protection (CBP) officials (“customs officials”) to—without probable cause or even reasonable suspicion—stop people entering the U.S. and require them to answer basic questions. (The law does not, however, allow regular police officers to do the same.)
(For more on this area of law, including as it applies to checkpoints and roving patrols, see our article on Search and Seizure at and Around the U.S. Border. That article also discusses the importance of legal consultation and links to a piece on the potentially complicating factor of state (rather than federal) law.)
This same Fourth Amendment exception applies to the functional equivalents of borders, such as airport entry points for international flights. Courts occasionally consider other places to be border functional equivalents. Even a checkpoint or the site of a roving patrol stop could be a functional equivalent depending on its proximity to the border and other factors.
During a border stop, customs officials are allowed to ask travelers ‘routine border’ questions. These questions are designed to help officials determine whether the person is allowed to enter the country or is transporting anything illegal. (U.S. v. Hudson, 210 F.3d 1184 (10th Cir. 2000); see Miranda and Border or Customs Questioning.)
Choosing to remain silent in this scenario may result in an extended detention for search and questioning, denial of entry into the U.S., or both. Note, however, that the ACLU of Arizona reports that a U.S. citizen selected for “a longer interview at the border” has the right to an attorney. The ACLU advises, “You may ask to have the questioning stop until you have an attorney present.” (The organization also explains the rules for non-citizens when it comes to issues like proof of lawful status in the U.S.)
At border stops on the road, without probable cause or reasonable suspicion, customs officials can search the interior of vehicles, including belongings. They can also conduct limited searches of drivers and passengers. More intrusive body searches and searches of inner compartments of vehicles may require reasonable suspicion or even a warrant. (For border searches in the airport context, see Laptop Searches at International Borders.)
These searches sometimes turn up evidence of crime that’s unrelated to immigration. Suppose, for example that drug-sniffing dogs alert a customs official to the presence of narcotics. The customs official may now be free to question the traveler about non-immigration, narcotics offenses. The official may also have authority to arrest the traveler, or might bring in local law enforcement for that purpose.