Originally Posted by theogt
You own the phone. You don't own the software. If you want to completely erase the software (and there was some way to do that), you could. That's not illegal.
It's not illegal to 'jailbreak' your device (or 'root') and modify settings other than the SIM. Also, not sure if still true, but it was possible to 'unlock' your phone with a hardware mod-leaving the software unaltered--so should that be illegal too?