The same way monero is banned in Australia - you don't allow exchanges to offer it to your citizens, and for them to cash it out. This can't stop everyone but a

The same way monero is banned in Australia - you don't allow exchanges to offer it to your citizens, and for them to cash it out. This can't stop everyone but as exchanges require KYC for cash deposits/withdraws it can curb the majority of the usage especially for speculation purposes. For a US example, look at how binance.com is banned in the US and imagine the same but for every exchange. If anything banning all of crypto is easier than banning a specific crypto and payment operators are pretty friendly to LE.