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.
There's a proof if the website has been hacked since the hacker is leaving his trace e.g. unauthorized connection and device, DDOS attack, regain access, changing password etc. Obviously the developer can create such drama, but it's matter of the government to trust the mixer claim or not.
Even there's no official laws and regulations for mixer, but we all know government always fight against of privacy and money laundering matter. It's just a matter of time mixer will be more regulated or they will ban all mixers.