How does the All Writs Act of 1789 give the FBI power to compel Apple to unlock Syed Farook's iPhone?

The All Writs Act of 1789 is part of the statute that created the federal judiciary. It has never been overturned, in all its years, and so it is still perfectly good law.  It allows a federal court to issue an order, to put it simply, which might seem like something that would not be necessary, but the reason for the need for this lies in the issue of over whom a court has jurisdiction. ...

The All Writs Act of 1789 is part of the statute that created the federal judiciary. It has never been overturned, in all its years, and so it is still perfectly good law.  It allows a federal court to issue an order, to put it simply, which might seem like something that would not be necessary, but the reason for the need for this lies in the issue of over whom a court has jurisdiction.  As a matter of course, when people go to court, a plaintiff versus a defendant or the state versus a defendant, the court can issue orders to the parties because it has jurisdiction over the parties. So, for example, the court can issue a subpoena to a plaintiff or defendant for records.  They must comply, even if it is a question of having to write new software to do so because the court has clear authority over them as parties. However, Apple is not a party in any proceeding in the court. It is a third party that in some way has nothing to do with what is going on, which is an investigation into the acts of an alleged terrorist. The All Writs Act is the mechanism by which the government has chosen to force Apple to provide the evidence it seeks.  Whether or not a court should be able to order a third party, over which it has had no jurisdiction at all, is a question that is of concern in a democracy, since any federal court anywhere could issue a sweeping order that would require great inconvenience, great expenditure, great loss of security, or actual harm to the customers of the third party.  Since the government has chosen to invoke the All Writs Act in this manner, the specter of these potential consequences has been raised, legitimately, in my own opinion, and while getting any kind of precedent from the Supreme Court right now is problematic, there is some likelihood that Apple will challenge the government's use of the Act all the way to the Supreme Court.