We all know about hacks, scams, password leaks and all the shit that's happening in the crypto world and we also see lots of scammers using mixers to eradicate the possibility of them being caught at all (though there are traces, but using mixer saves these scammers at the least, not intentionally).
Now, let's say that a hack happened some day at some exchange for about $300 million (or even $3 million, just e.g.), and the exchange immediately opens up about the hack. For a second, just think that the scammer keeps the coins in his wallet and doesn't move them for some time, however FBI and other major authorities are aware of this hack and they give orders to mixers that if a specific address is provided to the mixers (if they know exactly on which address the hacker has kept the coins), and they ask them to immediately report them about the same, then let me ask some questions:
1. Do mixers know where they're getting a deposit from?
2. If yes, will they co-operate here with the officials and let them know about the deposit?
3. If they do, how will they stop the scammer from moving his funds out of their mixer?
Let's suppose a hacker is reading this. What will be his course of action now. Since the Authorities have asked mixers to keep an eye on this address and do not entertain any request of mixing from this address, the hacker can easily create one or more brand new bitcoin addresses and move the funds to those newly created address. Then he can move the coins from that address to the mixers and mix the coin without any issues.
Secondly, no government have officially allowed to operate the mixers and therefore they have no legal right to dictate the mixers on what to do and what not to do.