I'd personally look to how governments around the world have tried to deal with Bittorrents.

1) Shutting down big torrent sites by modifying laws (for example, making linking to torrents illegal)

2) ISPs blocking the big sites domains like piratebay

3) Fining consumer users (who failed to be anonymous with VPNs and other tools)

4) Attacking the big users of the network (seed boxes, pirate groups or in the context of BTC: miners)

The other approach is make the conversion of state currency into BTC illegal. But the implications of that are unclear. Would people adopt a different crypto-currency? Would all crypto-currencies be banned? Could a BTC black market still exist like drugs?