Xmr is also becoming illegal in some countries. Mixers aren't illegal yet, as far as I know.
It would not really be possible to make using a mixer illegal.
If you send coins to a third party, you cannot control what they do with the coins. It is also difficult to know if you sending coins to a different wallet of yours is sending the coins to yourself or to a third party. If you receive coins from someone, you cannot control if they previously received the coins from a mixer. If you move coins from one wallet of yours to another, it is difficult to know if you are receiving the coins from a third party or are moving your own coins.