Shut down exchanges, don't let vendors accept it, and threaten citizens with jail time if found trading. They're not going to be able to get rid of it completely, but these should be enough to discourage 99% of the population to just drop it. Blocking Bitcoin itself at the protocol level alone would simply be too much of a hassle and has workarounds.
I disagree. Regulations in a country can certainly prevent the running of exchanges in that country as well as foreign exchanges or similar providers from servicing that country, but it is effectively impossible to block it completely because of its decentralized nature. Even the Great Firewall would not be able to block new sites that transact in Bitcoin and even if the bitcoin protocol itself is blocked in a country, it would only affect full nodes running on people's computers. They would literally have to ban every site accepting bitcoin and even then, bitcoin can also be transacted in person thanks to the crypto technology being online-independent. All that is needed is a valid transaction to be generated, whether online or offline, and someone, not necessarily the sender, to broadcast that transaction.
There simply isn't enough reason that could discourage people from using Bitcoin.