If you possess a cellphone on U.S. soil, the Fourth Amendment generally prevents law enforcement officials from searching your phone's contents without a warrant. But what happens if you carry a cellphone at the U.S. border while returning from a trip outside the country? Does the Fourth Amendment also stop border agents from warrantlessly snooping inside your device?

Not according to a pair of recent federal court opinions. "Border searches never require a warrant or probable cause," said the U.S. Court of Appeals for the 11th Circuit in a 2018 case, United States v. Vergara. That ruling centered on a U.S. citizen whose cellphones were subjected to warrantless forensic searches at the border, a highly intrusive procedure that typically involves retrieving deleted files and other inspections of a phone's digital records.

The U.S. Court of Appeals for the 9th Circuit reached a similar conclusion about warrantless cellphone searches at the border last week. "Border officials may conduct suspicionless manual searches of cell phones," the 9th Circuit held in United States v. Cano, "but must have reasonable suspicion before they conduct a forensic search." Unlike probable cause, which is the standard required for obtaining a search warrant, reasonable suspicion is a more lenient rule that lets law enforcement officials conduct searches without getting a warrant first.

The U.S. Supreme Court has long recognized a "border search exception" to the Fourth Amendment's normal warrant requirement. But the Court has yet to address whether that exception deserves to hold sway in the current era of smartphones and related high-tech devices.

It is one thing, after all, to let border agents rummage through your suitcase or through the trunk of your car without a warrant. It is something else to let those same agents download and examine every digital record on your cellphone—a treasure trove of highly sensitive personal information—without at least getting a warrant first.

Judge Jill Pryor, the lone dissenter in the Vergara case, suggested a good way for the federal courts to handle the issue going forward. "Due to the extreme intrusion into privacy posed by a forensic cell phone search," Pryor wrote in her Vergara dissent, "my answer to the question of what law enforcement officials must do before forensically searching a cell phone at the border…'is accordingly simple—get a warrant.'"