If anything the regulatory solution would be to find the ways in which demand for cryptocurrency exists because of failures in the existing financial system, and fix them so that the existing financial system can satisfy them. Allow bank accounts that work exactly like coin wallets, but rely on the banking system rather than PoW.

An obvious example is the existence of pseudonymous digital payments. Given that cryptocurrency already exists, and will continue to exist for all illicit activities even if you ban it, you might as well let people open numbered accounts at a bank.

Do this for any other advantage cryptocurrency has over the existing banking system and there is no more demand for cryptocurrency. And without demand, the price crashes and people stop burning coal to mine it.