FBI can't force Apple to unlock iPhone, NY judge rules

He said the help the US government was seeking from Apple could not be considered "agreeable to the usages and principles of law".

"The implications of the government’s position are so far-reaching – both in terms of what it would allow today and what it implies about Congressional intent in 1789 – as to produce impermissibly absurd results,” the judge said.

Orenstein said the government's reading of the All Writs Act was so expansive and "in particular, in such tension with the doctrine of separation of powers" that it would cast doubt on the Act's constitutionality.

He also noted the US Congress had considered and rejected a bill that would specifically force Apple to co-operate with the FBI in similar situations, meaning it could not now push for powers it declined to introduce.

"The relief the government seeks is unavailable because Congress has considered legislation that would achieve the same result but has not adopted it," Orenstein said.

While the ruling has no direct impact on the San Bernadino case currently being heard in a California district court - in which the FBI is pushing for access to the iPhone belonging to shooter Syed Farook - Apple is likely to cite the NY ruling in that legal battle.

It also potentially provides Apple a stronger platform for appeal should the California district court rule in the FBI's favour.

FBI director James Comey and Apple general counsel Bruce Sewell are scheduled to appear before a congressional hearing tomorrow.