1. This is quickly getting into the philosophy of law. Every case can be struck down by either appeal or a later case overturning precedent. I think such cases should be thought of as "it was illegal, but now it has been changed by the court". So once someone's lost, we call their actions illegal until they appeal and win.
2. You said that complying would open the door to doing it for other phones. In that regard, complying with an icloud request also opens the door to complying with future icloud requests. The fact that it creates the ability (for Apple) to do it later has no effect on legalities.
There may be a difference on undue burdens, but that's a different point. Your point would still be invalid. " creating new software for FBiOS is an undue burden, but creating new software to download a user's icloud data isn't " is a different argument than "creating new software means we can use it again later". The latter is the argument you made, and it doesn't differentiate between icloud and FBiOS.
If we're concerned the FBI will take the software and use it without a warrent, Apple was given the option to do everything on their own premises and just give the FBI the data/unlocked phone when done.
> You said that complying would open the door to doing it for other phones. In that regard, complying with an icloud request also opens the door to complying with future icloud requests.
There is one crucial difference. In the iCloud case, the government must ask Apple any time they want to get iCloud user data. Each time, Apple can verify that they have a court order before doing the work. So it's "stateless" in that the first request doesn't "open the door" for later requests.
In the iPhone case, the government is asking for an OS (signed by Apple) that can be flashed onto any device. This new OS would have a giant backdoor that disables all the protections of an iPhone. We all know there is no way to prevent this OS from being used elsewhere, for other uses. This is not stateless -- once Apple creates this OS, there is no going back, all phones are now insecure.
Every update to any iOS device (well, any since iPhone 3GS) requires a signature unique to that device. Since iOS 5, it also includes a nonce generated on device at the time of upgrade, so you can't even replay the signature, it needs to be signed at the time you install the new version.
This is why you can't downgrade to earlier versions of iOS after Apple stops signing them.
2. You said that complying would open the door to doing it for other phones. In that regard, complying with an icloud request also opens the door to complying with future icloud requests. The fact that it creates the ability (for Apple) to do it later has no effect on legalities.
There may be a difference on undue burdens, but that's a different point. Your point would still be invalid. " creating new software for FBiOS is an undue burden, but creating new software to download a user's icloud data isn't " is a different argument than "creating new software means we can use it again later". The latter is the argument you made, and it doesn't differentiate between icloud and FBiOS.
If we're concerned the FBI will take the software and use it without a warrent, Apple was given the option to do everything on their own premises and just give the FBI the data/unlocked phone when done.