https://en.wikipedia.org/wiki/All_Writs_Act
"(a) The Supreme Court and all courts established by Act of Congress may issue all writs necessary or appropriate in aid of their respective jurisdictions and agreeable to the usages and principles of law.
(b) An alternative writ or rule nisi may be issued by a justice or judge of a court which has jurisdiction."
a reasonable legal ground in this case to demand from a company to develop anything, in this case a special version of the operating system? Does this act mean "we can order anything to anybody"? Especially when there is "the Communications Assistance for Law Enforcement Act of 1992."
If anything goes, as "All Writs" is tried to be used by the FBI now, we don't need any other laws. "All Writs" rules.
Based off of the ruling handed down by the judge, it sounds like you could only rule that the work demanded of Apple is too onerous... I feel like that won't accomplish much though. I feel like this situation is pretty orthogonal to a ruling against any "Mandatory Backdoor" laws (which is the holy grail for us at this point)