Oh man... I didn't know they were illegal to keep! But I guess you just tlwt him live out his life in your tank and don't tell anyone
Pretty cool your able to keep him.
I'm usually completely against not following the laws but you didn't know it sounds like and now that you do there isn't much you can do about it.
If officials found out they would probably kill it and there is no need to kill it while it's being kept in a nice setup.