United States Border Patrol interior checkpoints
The United States Border Patrol operates 71 traffic checkpoints, including 33 permanent traffic checkpoints, near the southern border of the United States. The stated primary purpose of these inspection stations is to deter illegal immigration and smuggling activities. After the September 11 attacks in 2001, they took on the additional role of terrorism deterrence. These checkpoints are located between 25 and 75 miles (40 and 121 km) of the Mexico–United States border along major U.S. highways. Their situation at interior locations allow them to deter illegal activities that may have bypassed official border crossings along the frontier. The checkpoints are divided among nine Border Patrol sectors. There are a number of Border Patrol checkpoints in the northern border states (such as New York or Maine), within 100 miles (160 km) of the Canada–U.S. border.
The checkpoints are described as "the third layer in the Border Patrol's three-layer strategy", following "line watch" and "roving patrol" operations near the border. According to the U.S. Government Accountability Office,
"Border Patrol agents at checkpoints have legal authority that agents do not have when patrolling areas away from the border. The United States Supreme Court ruled that Border Patrol agents may stop a vehicle at fixed checkpoints for brief questioning of its occupants even if there is no reason to believe that the particular vehicle contains illegal aliens. The Court further held that Border Patrol agents "have wide discretion" to refer motorists selectively to a secondary inspection area for additional brief questioning. In contrast, the Supreme Court held that Border Patrol agents on roving patrol may stop a vehicle only if they have reasonable suspicion that the vehicle contains aliens who may be illegally in the United States—a higher threshold for stopping and questioning motorists than at checkpoints. The constitutional threshold for searching a vehicle is the same, however, and must be supported by either consent or probable cause, whether in the context of a roving patrol or a checkpoint search."
Under US law, people who enter the US without inspection (EWI) can be subjected to expedited removal if they are found within 100 miles of the border. This power has been subject to heavy criticism by the American Civil Liberties Union.
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