Nothing's stopping governments from doing this, but this should be fairly easy to bypass for the people involved as they can always generate new addresses. A marked address is essentially useless though, as authorities are likely willing to burn through resources to trace transactions with blockchain analysis.


It has always been bad practice to reuse addresses, so if you have reason to worry about this, you can simply use a different address for each transaction. It's very unlikely for them to tag addresses with very few transactions.