The filing represents Apple's first official response since the judge's order last week and builds upon arguments voiced by the company's chief executive and supporters.

The Justice Department is proposing a 'boundless interpretation' of the law that, if left unchecked, could bring disastrous repercussions for digital privacy, the company warned in a memo submitted to Magistrate Sheri Pym.

“The government says, 'Just this once' and 'Just this phone'. But the government knows those statements are not true," lawyers for Apple wrote on Wednesday.
    
The dispute broke into public view last Tuesday when Pym directed Apple to help the FBI gain access to a phone used by one of the assailants in the San Bernardino, California, attacks.
    
The filing was made the same day that FBI Director James Comey defended the government's approach during separate appearances on Capitol Hill, where he stressed that the agency was seeking specialized software for only one phone as part of an ongoing terrorism investigation.

The Justice Department wants to bypass some security features on the iPhone so that it can try as many passcodes as possible without the data being erased.