The U.S. Court of Appeals for the Fifth Circuit in U.S. v. Molina-Isidoro recently issued an encouraging opinion related to the digital privacy of travelers crossing the U.S. border.

EFF filed an amicus brief last year in the case, arguing that the Supreme Court’s decision in Riley v. California (2014) supports the conclusion that border agents need a probable cause warrant before searching electronic devices because of the unprecedented and significant privacy interests travelers have in their digital data. In Riley, the Supreme Court followed similar reasoning and held that police must obtain a warrant to search the cell phone of an arrestee.

In U.S. v. Molina-Isidoro, although the Fifth Circuit declined to decide whether the Fourth Amendment requires border agents to get a warrant before searching travelers’ electronic devices, one judge invoked prior case law that could help us establish this privacy protection.

Ms. Molina-Isidoro attempted to enter the country at the port of entry at El Paso, TX. An x-ray of her suitcase led border agents to find methamphetamine. They then manually searched her cell phone and looked at her Uber and WhatsApp applications. The government sought to use her correspondence in WhatsApp in her prosecution, so she moved to suppress this evidence, arguing that it was obtained in violation of the Constitution because the border agents didn’t have a warrant.

Unfortunately for Molina-Isidoro, the Fifth Circuit ruled that the WhatsApp messages may be used in her prosecution. But the court avoided the main constitutional question: whether the Fourth Amendment requires a warrant to search an electronic device at the border. Instead, the court held that the border agents acted in “good faith”—an independent basis to deny Molina-Isidoro’s motion to suppress, even if the agents had violated the Fourth Amendment.

The Fifth Circuit presented two bases for its finding of “good faith”—factual and legal. The factual basis of the agents’ “good faith” was that there was probable cause to support a search of Molina-Isidoro’s phone. The finding of drugs in her luggage, according to the Fifth Circuit, “created a fair probability that the phone contained communications with the brother she supposedly visited (or whoever was the actual source of the drugs) and other information about her travel to refute the nonsensical story she had provided.” The legal basis of the agents’ “good faith” was pre-Riley case law that generally permits warrantless and suspicionless “routine” searches of items travelers carry across the border. While the court did not rule on whether Riley requires a warrant for border device searches, the court did emphasize that a leading Fourth Amendment legal treatise recognizes that “Riley may prompt a reassessment” of the question.

Additionally, Fifth Circuit Judge Gregg Costa issued an instructive concurring opinion. While he agreed with the decision to let the WhatsApp evidence stand, based on the border agents’ “good faith,” he made two key points we have made in our own briefs.

First, Judge Costa considered whether the traditional primary purpose of the Fourth Amendment’s border search exception—customs enforcement—justifies conducting warrantless, suspicionless searches of electronic devices. As we have argued, the link between these ends and means is very weak. Judge Costa agreed: “Detection of … contraband is the strongest historic rationale for the border search exception.” Yet, “Most contraband, the drugs in this case being an example, cannot be stored within the data of a cell phone.” He concluded, “this detection-of-contraband justification would not seem to apply to an electronic search of a cellphone or computer.” We made the same argument in our amicus brief: “Just as the Riley Court stated that ‘data on the phone can endanger no one,’ physical items cannot be hidden in digital data.”

Second, Judge Costa considered whether an “evidence-gathering justification” could support warrantless, suspicionless border searches of electronic devices. He questioned this, citing an 1886 Supreme Court customs case, Boyd v. U.S., which we also cited in our amicus brief. The Boyd Court held:

The search for and seizure of stolen or forfeited goods, or goods liable to duties and concealed to avoid the payment thereof, are totally different things from a search for and seizure of a man's private books and papers for the purpose of obtaining information therein contained, or of using them as evidence against him.

In other words, while border agents have an interest in preventing the importation of physical contraband, they have at most a much lesser interest in searching papers to find evidence of crime. Judge Costa seemed persuaded by this holding in Boyd, especially given the unprecedented privacy interests modern travelers have in their digital data, stating:

[Boyd’s] emphatic distinction between the sovereign’s historic interest in seizing imported contraband and its lesser interest in seizing records revealing unlawful importation has potential ramifications for the application of the border-search authority to electronic data that cannot conceal contraband and that, to a much greater degree than the papers in Boyd, contains information that is “like an extension of the individual’s mind”…

While we would have liked the Fifth Circuit to affirmatively hold that the Fourth Amendment bars a border search of a cell phone without a probable cause warrant, we’re optimistic that we can win such a ruling in our civil case against the U.S. Department of Homeland Security, Alasaad v. Nielsen, challenging warrantless border searches of electronic devices.