Federal prosecutors said they will continue their attempt to compel Apple to unlock a seized iPhone 5S running iOS 7 even after the defendant in the relevant felony drug case pleaded guilty

On Thursday, defendant Jun Feng pleaded guilty to one count of conspiracy to distribute and possess with intent to distribute methamphetamine. Feng was originally charged with three counts of possessing and distributing methamphetamine. As part of the government's effort to convict Feng, the feds wanted Apple to unlock a seized iPhone 5S belonging to Feng—but Apple objected.

On Friday, United States Magistrate Judge James Orenstein said in a court filing that he is confused why prosecutors are still trying to compel the tech giant:

In light of the fact that the defendant against whom evidence from the subject telephone was to be used has pleaded guilty, I respectfully direct the government to explain why the application is not moot. To the extent the response requires the disclosure of information occurring before a grand jury, the government may file its response under seal, along with a redacted version suitable for public access.

The government's continued pursuit could suggest that it believes that Feng's phone may contain data relevant to another ongoing case. Feng was charged in conjunction with six other defendants.

"Perhaps they will argue they want see what is on the phone for sentencing," Jennifer Granick, an attorney and the head of the Stanford Center for Internet and Society, told Ars by e-mail. "But that type of information is likely less relevant in a drug case like this one than in other kinds of cases. Perhaps they hope to get a ruling they can appeal, and they don’t want to have to start over again. But that strategy doesn’t mean that this application isn’t moot."

Writ large

If Feng's phone had iOS 8 or later installed—as 90 percent of iPhones do—this entire issue would likely be moot. Apple now enables full encryption by default, and the company specifically said the move happened "so it's not technically feasible for us to respond to government warrants for the extraction of this data from devices in their possession running iOS 8."

But citing an 18th-century law known as the All Writs Act, federal prosecutors had gone to the judge and asked him to force Apple to unlock the phone. At its core, the All Writs Act simply allows courts to issue a writ, or order, which compels a person or company to do something. In the past, feds have used this law to compel unnamed smartphone manufacturers to bypass security measures for phones involved in legal cases. The government has previously tried using this same legal justification against Apple as well.

With the Feng case, the judge invited Apple into the courtroom to present arguments as to why the judge should not order it to comply. It was the first time Apple was invited to speak against the government's request, and the company made a compelling argument as to why it should not be forced to do prosecutors' bidding.

"The government’s proffered reading of the All Writs Act, if carried to its logical conclusion, leads to disquieting results," Ken Dreifach, an attorney representing Apple, wrote in his reply to the government earlier this month. "For example, if the government wanted to crack a safe, it could require the safe’s manufacturer to take possession of, or even travel to the location of, that safe and open it," he continued. "If the government wanted to examine a car, it could send the car to the manufacturer and require the manufacturer to perform the examination. The government could seemingly co-opt any private company it wanted to provide services in support of law enforcement activity, as long as the underlying activity was authorized by a warrant. The All Writs Act does not confer such limitless authority."