Remember that whole big mess with Tornado cash? Well if you don't to sum it up it's a platform that lets you put crypto in and then later take it out. But the mix of sending it to the pool and taking it back out makes it near impossible to tell who took it out. You might know who put the money into the pool but if different amounts are taken back out it's pretty much impossible to track and know. Unless well only one person is using it.
The more people that use the platform the more confusing and harder to track it becomes and well governments that track everything didn't like this so much. What's really crazy is that it's the simplest thing ever. Nothing really confusing or hard about it at all and yet can foil tracking of crypto assets.
The ruling now is that tornado judgment has been reversed which is the operation of the site. Now the owner is still in jail due to money laundering charges but the site in itself as a decentralized entity has been ruled that the courts have over reached.