Apple talks a big game about its commitment to customer privacy, but the words mean something. This week, the company told a federal judge that it’s actually impossible to unlock a password-protected iPhone running iOS 8 or later.

The Justice Department has asked U.S. Magistrate Judge James Orenstein to compel Apple to allow the government a back door into iPhones for law enforcement purposes. Apple’s response:

“In most cases now and in the future, the government’s requested order would be substantially burdensome, as it would be impossible to perform. For devices running iOS 8 or higher, Apple would not have the technical ability to do what the government requests—take possession of a password protected device from the government and extract unencrypted user data from that device for the government. Among the security features in iOS 8 is a feature that prevents anyone without the device’s passcode from accessing the device’s encrypted data. This includes Apple.”

The company filed a brief with Judge Orenstein Monday night, according to the Wall Street Journal.

Why this matters: Apple continues to affirm that the information stored on your iPhone is accessible only to you. While privacy policies are reassuring, Apple backs up its words with technology. This prevents the company from offering services that its competitors do—like powerful photo analysis—because it actually can’t access your data.

“We think encryption is a must in today’s world,” Apple CEO Tim Cook said Monday during Wall Street Journal’s WSJDLive technology conference. “No back door is a must.”

iOS 7 not as secure

Investigators are pursuing a back door into a specific iPhone, not all iPhones, though the request has broad implications. The phone in question is running iOS 7, which means Apple can “extract certain categories of unencrypted data” like some files in native apps, but the company said it would rather not.

“Forcing Apple to extract data in this case, absent clear legal authority to do so, could threaten the trust between Apple and its customers and substantially tarnish the Apple brand,” the company said in the brief filed Monday.

If your phone is running iOS 7, Apple said it can’t pull data from your email, calendar, or third-party apps, but your device isn’t quite as locked down as it would be on iOS 8 or 9.