For travelers in the American Southwest, brief Border Patrol interrogations at highway checkpoints are a familiar experience, courtesy of the “border search exception” to the Fourth Amendment. 

Omar Ruiz-Perez was stopped along Interstate 19, south of Tucson, on January 19, 2011. Using guidelines specifically developed to identify trucks smuggling illegal drugs, Border Patrol agents directed the defendant to a secondary inspection area where X-rays of the vehicle revealed a hidden compartment full of narcotics. They did not suspect him of carrying illegal immigrants.

As the Supreme Court put it in the 1985 case United States v. Montoya de Hernandez, “automotive travelers may be stopped at fixed checkpoints near the border without individualized suspicion” for the sake of immigration control. But in the 2000 decision Indianapolis v. Edmond, the Court cautioned that “we cannot sanction stops justified only by the generalized and ever-present possibility that interrogation and inspection may reveal that any given motorist has committed some crime.”

In April U.S. District Judge Jennifer G. Zipps nevertheless approved the Tucson search, writing that “agents could have objectively believed that Defendant’s truck, based on its size, contained evidence of alien smuggling.” Since the federal government applies the border search exception anywhere within 100 miles of an international boundary, the logic of this ruling potentially subjects two-thirds of the U.S. population to roadblocks aimed at revealing violations of any law, as long as law enforcement officials invoke immigration.