Any Party Whose Assistance Is Deemed Necessary

From Apple's response:

The government says: “Just this once” and “Just this phone.” But the government knows those statements are not true; indeed the government has filed multiple other applications for similar orders, some of which are pending in other courts. And as news of this Court’s order broke last week, state and local officials publicly declared their intent to use the proposed operating system to open hundreds of other seized devices—in cases having nothing to do with terrorism. If this order is permitted to stand, it will only be a matter of days before some other prosecutor, in some other important case, before some other judge, seeks a similar order using this case as precedent. [pg. 3]
In addition, compelling Apple to create software in this case will set a dangerous precedent for conscripting Apple and other technology companies to develop technology to do the government’s bidding in untold future criminal investigations. If the government can invoke the All Writs Act to compel Apple to create a special operating system that undermines important security measures on the iPhone, it could argue in future cases that the courts should compel Apple to create a version to track the location of suspects, or secretly use the iPhone’s microphone and camera to record sound and video. And if it succeeds here against Apple, there is no reason why the government could not deploy its new authority to compel other innocent and unrelated third-parties to do its bidding in the name of law enforcement. For example, under the same legal theories advocated by the government here, the government could argue that it should be permitted to force citizens to do all manner of things “necessary” to assist it in enforcing the laws, like compelling a pharmaceutical company against its will to produce drugs needed to carry out a lethal injection in furtherance of a lawfully issued death warrant, or requiring a journalist to plant a false story in order to help lure out a fugitive, or forcing a software company to insert malicious code in its autoupdate process that makes it easier for the government to conduct court-ordered surveillance. Indeed, under the government’s formulation, any party whose assistance is deemed “necessary” by the government falls within the ambit of the All Writs Act and can be compelled to do anything the government needs to effectuate a lawful court order. While these sweeping powers might be nice to have from the government’s perspective, they simply are not authorized by law and would violate the Constitution. [pg. 26]

This is why the government must not prevail here.

Oh, Apple has a bunch of other fantastic reasons in there too. Read through the response. It is amazingly well explained, clear, and not terribly legal (at least through the end of the main document). In fact, after reading it thoroughly, I don't see how the government can hope to win here in the end.

I don't think they want to win. I think they want a fight. Hopefully one that goes all the way to the Supreme Court (and the fight over Scalia's seat makes it all the more delicious). And this gives congress and the next president legal "cover" to push for "reform" in the next term, after the elections. They're stirring up controversy in an election year. And, frankly, I think it is pretty overtly targeted more at one party than the other. Though they'll be happy for bipartisan help when they push for their New and Improved Patriot Act III - Smartphone Edition (and, sadly, I don't think Mrs. Clinton has done much to illustrate restraint here either).

Which is as sad as it is absurd. It obviously won't work. It can't actually work to do what they say they want (to fight the terrorists), because you know, you can't outlaw math.

But you'll sure hurt American technology companies in the global market while you're trying. And who wins then? Mostly China.