Tlhokaina Would it be possible for mobile carriers to block devices running what would be considered an 'illegal' ROM?
They already do block devices from running alternative OS's - it's called OEM locking. Verizon is a notorious example of that.
However they do not block running alternative OS's for being "illegal" or controversial, or what-have-you. They block OEM unlocking to keep their profits (in the case of a phone contract, where you're still buying the phone from them)