Legally forcing someone to use their finger to unlock their phone

The LA Times:

Authorities obtained a search warrant compelling the girlfriend of an alleged Armenian gang member to press her finger against an iPhone that had been seized from a Glendale home. The phone contained Apple’s fingerprint identification system for unlocking, and prosecutors wanted access to the data inside it.

This is a fork in the road. One path leads to hacking a phone to override the passcode. This path leads to using the national fingerprint database in reverse, generating a fingerprint, on demand, to unlock a specific phone.