These entities:

https://home.treasury.gov/policy-issues/financial-sanctions/...

> As a business accepting Ethereum, how do I know whether my customer has used Tornado Cash in the past?

Why does that matter? You need to make sure you don't break sanctions. You don't have to worry about other people.

I guess they just don't really understand how Ethereum works? The minute whoever controls those addresses transfers the ETH out to some other addresses (a cheap/trivial operation) the sanctions are obsolete.

Are you not phased at all by the inaneness of it?

It may seem inane if you assume that the only purpose of the sanction is to prevent the money from being transferred.

It could be that they have enough parallel information that they know who controls these addresses and they're just waiting for someone to violate these new sanctions :)

I doubt that. It's not possible to track which of the depositors withdrew. That's the whole point of the smart contract.

Within the realm of the blockchain, yes. But regulators do much of their work in meatspace. Smart contacts won’t protect you from information gathered elsewhere.

So you believe that there are certain people that the OFAC wants to arrest but can't, because those people haven't committed a crime / aren't criminals.

So they make up a law that will basically force people to chose between losing their life savings or breaking the law. Some people will rightfully ignore the law and recover their money. The OFAC can now arrest those people...

I mean it's not impossible but I find it hard to believe that the OFAC would be that morally bankrupt.

I didn’t say any of that. I have no clue what they’re doing. The simple answer is that law enforcement rarely moves to prosecute with one piece of evidence, they often have multiple pieces. And they often use use one lead to find others who are involved. And if they can make it more difficult for people to continue crime, they will. There are often many factors at play.