This is a very strange scenario you're describing where: a) the global economy has moved onto the blockchain; b) the government has repealed all the major points of the legislation that we were originally talking about; c) the government has also exhibited complete dictatorial control over the logic of the major stablecoins, and banned all of the functionality that makes them actually useful; d) people decide not to use the blockchain's native token to settle transactions for some reason.

Remember, issuers want people to use stablecoins because they get to invest the funds in treasuries and hold onto the interest. If everything is blacklisted then no one will want to use them and the issuer won't make any money.