TornadoCash is a smart contract, so there is not really a way to enforce the sanction.

Plus, there is not really a way to tell who creates a smart contract if you cover your tracks well enough.

This sanctions stuff is smoke and mirrors for the government to try and convince themselves they are capable of doing something.

The most realistic approach is for major chains to go POS and the major validators and other important pieces of the puzzle to need a lot of resources to the point where they become businesses and are on the governments radar (and by extension they would need to comply with regulations).

But because everyone knows that is a natural consequence of POS, it is exactly why no reasonable person would be on board with a transition to it.