You could cascade the sanctions so any addresses touched by sanctioned addresses becomes sanctioned too; that leads you open to trolling and abuse where a sanctioned address sends money to celebrities to impact them. This could probably be dealt with by saying anyone who uses an obvious Tornado-style contract that's been sent money from XYZ address is illegal, so you don't end up with the trolling, but I don't know for sure how that'd work.
Is it possible to design an algorithm that comes to a consensus on what new address to use faster than the legal system can sanction them?