There's a lot of misinformation and misunderstanding going on with respect to the current dispute between the Obama Justice department, and Apple, with respect to the San Bernardino terrorist phone that the government wants to unlock.
Permit me to explain what's really going on here, with a minimum of math and science, and why this is terrible, All Writs Act or no.
First off, the All Writs Act doesn't really mean much. Here's the actual text of 28 USC §1651:
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.
Rough translation: Judges are allowed to order things that are legal, in support of matters before them that are legal. However the Obama administration wants this to be a total blank check, ignoring all the words after "jurisdictions." They want judges to be allowed to order anything not withstanding other laws, as long as it's in service of a legal warrant.
But here's the truth: If what Obama's lawyers are asking of Apple is "agreeable to the usages and principles of law," then we no longer live in a time of limited, Constitutional government. What they are asking for is a broad attack on the privacy of millions of Americans, permanently undermining the security of every iPhone in America (and the rest of the world).
How is that possible? How is what the government is asking, so ridiculously extreme? The iPhone has been designed to give a great deal of security to its contents, protecting the privacy of users who turn on all of the optional settings. If you ramp it up to the max, then everything on the phone is encrypted using strong, NSA-tested encryption, protected with a key. That key is then protected by the passcode you use. Which means that is the potential weak point in the system.
Apple allows you to protect that weak point, with a setting that will wipe the phone entirely, in the event that too many wrong passcodes are guessed. Further, Apple has code in there that will slow you down, if you guess too many wrong passcodes. Those features combine to plug the leak, and that's what the government is worried about. They want Apple to make them a special version of the iPhone's software, that will remove those options, allowing the government to rapidly test thousands of passcodes.
The Obama administration therefore is asking for a back door. They want the security features of the iPhone to be disabled for them. They want brand new software to be written by Apple for the sole purpose of defeating the security features in their own product. And once Pandora's Box is opened, then every iPhone on Earth, that people are relying on for security, is no longer safe.
Apple's taken great pains to secure the platform. The government is demanding it be made insecure with a back door around all that security, turning it into security theater. Obama must be stopped on this, All Writs Act or not, the Bill of Rights does not empower the government to unlock the iPhones of all Americans, in order to go after one filthy terrorist. This is exactly contrary to every principle we have.