That link is why tl;dr came to be. But have fun with that.
I read it just to see what the media (or at least the media I encountered) didn't tell us...
Here's what I learned: the power the gov't wants to claim in this case is power that was explicitly addressed in a bill that came up for consideration previously... and both the White House and Congress decided it was a bad idea... which means they already decided in advance that the FBI should not be able to make Apple do what they now want to make them do...
So, this is not some out-of-the-blue horrible surprise situation that nobody thought about before... the gov't had previously considered this very thing and had rejected the idea that they should have the coercive right they are not claiming. What's out of the blue is not the scenario... what's out of the blue is the notion that the gov't can do this... because the gov't had already decided that (a) it didn't have this power, due to a previous law (CALEA = Communication Assistance for Law Enforcement Act) which explicitly said the gov't could not make Apple do what the FBI is now trying to make them do, and (b ) if the gov't needed to have this power, they needed a new law (CALEA II) to modify the previous law that said they didn't, and (c ) the gov't should not have that power, which is why the proposed new law was neither encouraged by the White House nor passed by the Congress.
In other words, the FBI's lawyers are full of crap about this one... assuming the account provided by Apple's lawyers is correct. Whether their account is correct or not is something I don't know enough about to say...
EDIT: The way the FBI got the judge to issue the court order that Apple is fighting is they went to the judge with a request for an emergency order... which meant the judge had to rule having heard the FBI's side but without Apple having a chance to give the counter-argument... so, when the court rules on Apple's effort to fight this thing, it will be the first time the court has ruled after having heard both sides...