Earlier quoted context omitted.
Seems like a huge oversight to not let SIM cards disable certain types of encryption (that it knows the home network will never use). IIRC this is how downgrade attacks are prevented in EMV - the chip card will reject known-broken auth methods.
The FCC takes a dim view on 911 call failures. All phones must support disabling GSM encryption as a fail safe. Never disabling encryption would be “fail secure” (like door locks that remain locked during a power outage).
Emergency calls already have a bunch of exceptions that don't apply to regular traffic (e.g. you can use any network, heck you don't even need a SIM card) so allowing only those to be unencrypted shouldn't be too much of a stretch