What can be done is you can write the different trading platform that they're sending the coins to. In this way you can notify them that these were ill-gotten gains and that are illegal. In some cases those places may confiscate the coins. But very much like everyone else said short of this, it's the beauty and the pain of having a decentralized ecosystem like this. People are in charge of their own money, and there is no real safety nets besides your own. :/