The are probably existing laws against the abuse depending on your country. They're just not enforced.
It's much easier to trace than IP traffic as well. Every internet telco will have full logs of each connection.
It is true though if the FCC started handing down fines that VoIP providers would require insurance/bonding all the way up. That would not fix it all but would be a large jump forward.
We also need end-users to force the issue. File suits and complaints. Every time we'd receive a complaint the resolution was "we blocked that number" and "we have no further info". If there was someone pushing a lawsuit through then suddenly everyone up the supplier chain would hand over their customer info right to the real end-user.
Instead, the FCC runs silly programs like their Anti-Robo-Dialer thing.
Only the first party needs to know the answer. The enforcing org can ask the first telco: was it your subscriber who initiated? If yes, fine the subscriber. If not, repeat with the telco that sent the call. If the last telco knowingly helped, fine it as well.
> Even AT&T routes to dozens of providers for some calls and has no idea what is going where.
Lol. :-) Every single connection initiated exists in very detailed CDRs. That includes the path used as well, since they have to deal with billing other telcos for handling their calls and finding the right (cheap) path at the right time. Telcos either have full records, or they lost money. I can't think of a business with more detailed record of every single transaction they make. Probably even accounting is less strict.