In the latest case involving efforts to compel Apple to help law enforcement break encryption, the company said the court should simply rule the assistance is unnecessary and not authorised by law.

The case in a federal court in Brooklyn comes weeks after the FBI dropped a hotly contested effort to require Apple to weaken the security of an iPhone used by one of the shooters in last year's attacks in San Bernardino, California. In this case, Apple attorneys argued, the court can avoid a 'constitutional thicket' and rule on 'narrower grounds'.

The Justice Department earlier this month appealed a decision by a US magistrate in Apple's favor, saying it still wants the company to extract pictures, text messages and other digital data from an iPhone used by someone accused of trafficking in methamphetamines.
The case is one of several pending in US courts as lawmakers and others debate whether Apple and other tech firms should be required to help break strong encryption, which in many cases allows only the user to access data, with no 'keys' held by the company.

Apple said the government's interpretation of the All Writs Act, a 1789 law that gives the courts wide latitude to help law enforcement, was 'soundly rejected' by the magistrate's ruling.