American law enforcement has long advocated for universal “kill switches” in cellphones to cut down on mobile device thefts. Now the Department of Justice argues that the same remote locking and data-wiping technology represents a threat to police investigations–one that means they should be free to search phones without a warrant.

In a brief filed to the U.S. Supreme Court yesterday in the case of alleged Boston drug dealer Brima Wurie, the Justice Department argues that police should be free to warrantlessly search cellphones taken from suspects immediately at the time of arrest, rather than risk letting the suspect or his associates lock or remotely wipe the phone before it can be searched.

The statement responds to briefs made to the court by the Center for Democracy and Technology and the Electronic Frontier Foundation arguing that warrantless searches of cellphones for evidence represents a serious violation of the suspect’s privacy beyond that of a usual warrantless search of a suspect’s pockets, backpack, or car interior.

“This Court should not deprive officers of an investigative tool that is increasingly important for preserving evidence of serious crimes based on purely imaginary fears that police officers will invoke their authority to review drug dealers’ ‘reading history,’ … ‘appointments with marital counselors,’ or armed robbers’ ‘apps to help smokers quit,'” reads the statement written by DOJ attorney Donald Verrilli Jr., responding to specific examples cited by the CDT.

At another point in the brief, Verrilli adds that “searching an arrestee’s cell phone immediately upon arrest is often critical to protecting evidence against concealment in a locked or encrypted phone or remote destruction.”

That last statement strikes civil liberties advocates as especially ironic, given law enforcement’s enthusiasm for new requirements that all cellphones implement exactly that sort of “kill switch” as a bulwark against a rising tide of cellphone thefts. The technology lets cellphone owners remotely wipe or encrypt the data on their phone if it’s stolen, or kill the phone entirely so it can’t be used by the thief.

Law enforcement officials ranging from New York State Attorney General Eric Schneiderman to San Francisco District Attorney General George Gascón to several major city police commissioners have all pushed for a bill introduced in February by Minnesota Senator Amy Klobuchar requiring the kill switches in all smartphones.

“You have this weird scenario where law enforcement has demanded remote wiping be deployed,” says ACLU principal technologist Chris Soghoian, “and now they’re using that to also justify warrantless searches.”

In its brief, the Department of Justice describes those same wiping functions as dangerous tools for covering the tracks of criminals:

For example, in one California case,the members of a narcotics-trafficking organization “admitted that they had a security procedure, complete with an IT department, to immediately and remotely wipe all digital evidence from their cellphones.” And because remote-wiping capability is widely and freely available to all users of every major mobile communications platform, individuals have used the same tactic. That problem will only increase as mobile technology improves and criminals become more sophisticated.

But there are better ways to respond to the threat of evidence destruction on mobile phones than warrantlessly rifling through the devices’ data on the spot, argues Hanni Fakhoury, an attorney with the Electronic Frontier Foundation. He points out that it’s easier–and potentially less unconstitutional–to simply remove the phone’s battery, turn it off, or put it in a Faraday cage that blocks all radio communications while the police wait for a judge to sign a warrant.

He adds that the Justice Department has yet to prove that the remote wiping problem is a real issue. “The government can point to no actual statistics that show this is a widespread problem,” says Fakhoury. “And the reality is that most people don’t even have remote wiping technology on their phone.”

In its brief, the Justice Department also argues that regardless of the Court’s decision on warrantless access to the entire phone, police should at least be granted access to phones’ call logs. The brief references an argument known as the “third party doctrine,” that individuals don’t have a “reasonable expectation of privacy” for information shared with a third party like the phone company, so it’s not covered by the Fourth Amendment prohibition on warrantless searches.

“If this Court were to draw a special exception from that settled doctrine for information on cell phones…it should at least preserve officers’ authority to review information in which the individual lacks a significant privacy interest, such as information that is also conveyed to telecommunications companies,” the brief reads.

But that argument ignores the fact that the specific data being searched in this case isn’t actually held by the phone companies, but stored on the device itself, argues the ACLU’s Soghoian. If it were held by the companies, cops wouldn’t need to search the phone in the first place. “What matters isn’t just the information, but where they get it from,” says Soghoian. “They’re saying that there are certain things on your phone that have less protections than others under the law, which is crazy.”

Read the Department of Justice’s full brief to the Supreme Court below:

Warrantless Cell Phone Search Government SCOTUS Brief by Justin Kelly