[ikeboy]

All it would take is providers refusing to connect to anyone that supports spoofing. Let users report spoof calls, then blacklist those providers. Everyone will fall in line real quick. (You could also just fine them for each spoof, not cut them off completely, but enough so they won't want to offer it a service to their customers. Also, of course you announce this months in advance so everyone has a chance to stop supporting it first.)

Call forwarding is fine as long as the spoofed number is also associated with the caller. But anyone that lets people call using a number that's not theirs at all should be booted off.