The legal system lets them say "you already have the information? Great, give it to me". It doesn't let them say "you have to redesign your systems to collect information that you explicitly told your users you aren't collecting".

I don't have a direct citation for you, besides having seen this spoken about before, but a simple thought exercise should prove it: If the government could compel that sort of thing, then we wouldn't have end-to-end encrypted chat (including iMessage) and the government would have already compelled Apple to give the government a backdoor into iPhones.

I personally want the law to say that but:

The FBI took a different view in a recent court case referencing the All Writs act of 1789 https://en.wikipedia.org/wiki/FBI%E2%80%93Apple_encryption_d... but dropped it when they unlocked the device by other means., and the issue hasn't really made it through the court system, so it's unclear what the law requires.

Until a federal case gets to the appeals court level it basically won't establish any binding precedent in other cases under stare decisis.

Good news is the FBI doesn't write the law. My recollection is the general consensus was the FBI was severely overreaching and was going to lose their court case.

I mean that's what I think, but general consensus also doesn't write the law, unfortunately.

I think under the construct that computer code is a means of expression protected under the first amendment, the US government requiring Apple to implement a code change would be considered a form of compelled speech.