TexasCHLforum.com

"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. General Accounting Office,[2]

"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.[4] The Court further held that Border Patrol agents "have wide discretion" to refer motorists selectively to a secondary inspection area for additional brief questioning.[5] 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.[6] 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.[7]"