I wonder if the legal burden of compliance is on the phone manufacturer or on the cell phone service provider. The next step would be for the cell phone service provider to not accept non-compliant phones on to their network, and to require of the manufacturer that they remove that GPS on/off control from user control as a condition of compliance. Of course, with opensource code running on the phone, the service provider could place the burden back on Purism. This would likely result in either a lawsuit, or in the FCC deciding who needs to be the one to comply. Either way, if the government wants to track you badly enough, they will force all GPS tracking to stay active all of the time.
By the time things get this far, the government has to tip its hand about what their motive is. Do they only care about tracking you while you are on an active phone call? Or do they demand to track you all of the time? Because there is also that modem kill switch. Will the government want to take away your access to that switch also? Right now, this issue isn’t even a big enough issue to show up on anyone’s radar. But if enough people circumvent Google and Apple’s lockouts by going with Purism, then what? The law was passed for some reason.