Citizens' rights to be free from searches don't hold everywhere. At border crossings, as in airports, people can be searched by authorities as a matter of routine course. But what should the standard be for not just rummaging through a briefcase, but for when the government wants to dig deep into the files on our electronic gadgets—even looking at deleted files?

A "watershed" decision from a federal appeals court today ruled that the government must have "reasonable suspicion" to do such an intensive computer search. However, the judges also ruled that standard was met in the search in question, which involved child pornography being brought across the border from Mexico. The US Court of Appeals for the 9th Circuit, sitting "en banc," reversed a lower court's decision to suppress an intensive forensic analysis of a laptop belonging to a traveler, Howard Cotterman, which resulted in a discovery of child pornography.

The search started out as a "cursory review at the border but transformed into a forensic examination of Cotterman's hard drive." The court acknowledged it was a "watershed case" with implications for what kind of privacy rights all Americans can expect with regards to password-protected files on their computers.

A criminal history and password-protected files create “reasonable suspicion”

Border searches are an exception to the general principle, protected by the Fourth Amendment, that warrants be obtained. Still, a border is not an "anything goes" zone, as an 8-3 majority of the court emphasized in today's decision [PDF]. Searches still need to be based on a "reasonable suspicion."

Cotterman was returning to the US with his wife from a vacation in Mexico in 2007. In a routine check, a border computer system returned a hit for Cotterman—he was a sex offender, and had been convicted on several counts, including child molestation, in 1992. The agents then searched his car, and found two laptops and three digital cameras, which they also inspected. Those devices had several password-protected files.

The border agents suspected, based in part on the existence of password-protected files, that Cotterman may have been engaged in sex tourism. They interviewed him and his wife, and ultimately released them—but kept the laptops and one camera. The laptop was brought to an Immigration and Customs Enforcement office in Tucson, Arizona, where an ICE agent performed intensive forensic search on the laptops. On one laptop, the search found 75 images of child pornography in the "unallocated space" of the hard drive, which is where deleted data resides.

Cotterman was indicted on child porn charges. The judge overseeing his case ruled the evidence should be suppressed. Cotterman's 15-year-old history, combined with the mere presence of password-protected files, wasn't enough to justify a search under the "reasonable suspicion" standard. That judge's decision was reversed by an appeals panel, and now the case has gone to the full 9th Circuit, with a majority agreeing that the government did have a right to search the laptop.

The majority in today's ruling found that "the legitimacy of the initial search... is not in doubt." That search would have been fine, even without "particularized suspicion," a majority of judges held. But the intensive forensic examination that analyzed the whole hard drive presents a "difficult question," they acknowledged. Even though the rules are different at the border, searches must still be regulated somehow.

Still, the majority felt that on balance, the search was justified.

In defining the new standard, the majority recognized that technology has created a situation where a search of electronics has become much more intrusive over time. Judge Margaret McKeown wrote:

The amount of private information carried by international travelers was traditionally circumscribed by the size of the traveler’s luggage or automobile. That is no longer the case. Electronic devices are capable of storing warehouses full of information. The average 400-gigabyte laptop hard drive can store over 200 million pages—the equivalent of five floors of a typical academic library. ... With the ubiquity of cloud computing, the government’s reach into private data becomes even more problematic. In the “cloud,” a user’s data, including the same kind of highly sensitive data one would have in “papers” at home, is held on remote servers rather than on the device itself.

And while certain privacy rights are given up during travel, others are not.

"International travelers certainly expect that their property will be searched at the border," wrote McKeown. "What they do not expect is that, absent some particularized suspicion, agents will mine every last piece of data on their devices or deprive them of their most personal property for days (or perhaps weeks or even months, depending on how long the search takes). Such a thorough and detailed search of the most intimate details of one’s life is a substantial intrusion upon personal privacy and dignity."

Still, reasonable suspicion was found here, with the main factors being the fact that Cotterman had a history of sex offenses, and had password-protected files. "Although password protection of files, in isolation, will not give rise to reasonable suspicion, where, as here, there are other indicia of criminal activity," it becomes an important factor, wrote McKeown.

Dissents in multiple directions

Today's decision includes two dissents, arguing in different directions. One dissent, signed onto by three judges, argues that the decision actually makes it too hard for border agents to conduct searches. Those three argue that the government should be given wide clearance to perform searches at the border, and that the advent of new technology doesn't change that.

The government's job of stopping "drugs, bombs, or child pornography" from entering the country is a "Herculean task" and "requires that the government be mostly free from the Fourth Amendment's usual restraints on searches of people and their property," writes Judge Consuelo Callahan, a George W. Bush appointee. "The majority relies primarily on the notion that electronic devices are special to conclude that reasonable suspicion was required," Callahan continues. "The majority is mistaken."

She notes that the Supreme Court has only once required "reasonable suspicion" in the 125 years it has been reviewing border-search cases. "[C]ourtesy of the majority’s decision, criminals now know they can hide their child pornography or terrorist connections in the recesses of their electronic devices," she writes.

There's dissent even among the dissenters in this opinion. A second dissent, written by Judge Milan Smith, agrees that the majority was wrong to establish a "reasonable suspicion" requirement for searches at the border. But Smith goes on to argue there was also no reasonable suspicion to do the more intensive "extended border search" of Cotterman's computer at the Tucson facility, 170 miles away from the border.

"I fail to see how the agents had reasonable suspicion that Cotterman’s computer contained 'illegal files' based solely on his 15-year-old sex offense, travel to Mexico with his wife, and the 'ubiquitous' act of password-protection," wrote Smith. "Mexico is a popular travel destination for Californians, including those who travel to Mexico for its beaches, culture and weather, and not for its sex tourism."

"Under the doctrine of this case, the majority sweeps in thousands of innocent individuals whose electronic equipment can now be taken away from the border and searched indefinitely, under the border search exception," writes Smith.