I think they would not regulate the currency itself, is the places where they trade, we can already see the kyc that exchanges are asking for, that's a way to regulate, because with the kyc and you can start tracking the money and operations of that user.
The government certainly has a way to find out who the crypto owner is in his country, and tries to get revenue from crypto transactions. The government can request data from the crypto exchange, because from there the government will follow up according to the rules in the country.