Federal law grants U.S. Customs and Border Protection (CBP) the right to perform searches and seizures without warrant or probable cause “within a reasonable distance from any external boundary of the United States.” An external boundary is considered any international point of entry into the U.S., including international land borders and the coastline. The government has defined this reasonable distance as 100 air miles. This radius, emanating 100 miles out from all of the country’s external boundaries, is known as the border zone.
CBP can set up permanent and temporary checkpoints, patrol highways and board buses, trains and other vehicles anywhere within the border zone. The American Civil Liberties Union found that approximately 200 million people live in a border zone. Federal law grants CBP the right to enter private property, except “dwellings,” within 25 miles of an external boundary.
Still, the Fourth Amendment blocks arbitrary and warrantless searches and seizures of people and their property. Federal agents must establish they have reasonable suspicion of an immigration violation to perform searches or detain people. CBP’s activity within the U.S. interior has been the subject of a number of lawsuits.