As everyone said you can do anything other than reporting it to the authorities who confiscated the funds and maybe after the investigation ends they might return the funds to users who didn't do any violation using the mixing service.
Unless they have a ruling that they are going to do that, once a platform is marked part of money laundering and the people behind it are marked criminals they can treat all the funds confiscated as part of criminal activity you need a lawyer to act on your behalf that you've used mixing for good purposes, now this is another investigation if it's a huge amount of Bitcoin then go for it, you don't want to go on your life thinking you wasted a big amount of Bitcoin because you did not fight for it in the court.