Contrary to popular belief, Twilio is not exactly magic. They're great in that they put a simple, easy to understand API, and very low startup friction (painful signup almost more important than cost) to do things you knew were possible, but didn't want to deal with figuring out how to sign up for. They weren't necessarily the first one to do that either.

My point is, there are at least hundreds of providers you can get a voip line from, in addition to the many traditional carriers you could get conventional phone lines from; many of which are not really beholden to the courts of whichever jurisdiction you choose. Getting them all to agree not to provide service to one person is going to be hard; especially with the large networks of reselling resold traffic.

I would love to see some sort of regulation requiring some ability to trace down the origin of calls, though. There should be a way to track back which carriers (and their customers) involved when the recipient would like to press charges against the entity that placed the call (ex: the fraudulent callers from "The Windows" trying to "fix" my computer). There are valid reasons for anonymous calling, so safeguards should be in place, maybe just a star code (feature code) to indicate the last received call was spam, and a caller that generates a large number of reported calls is subject to investigation by the carrier and referral to law enforcement if appropriate.