[nostrademons]

Typically courts will void the contract if there's a material misrepresentation or fraud in a contract:

https://thebusinessprofessor.com/knowledge-base/voidable-con...

In cases of fraud, the deceived party may also bring a tort, which is awarded in USD. But as for the actual contract, the court would rule that it never occurred, and so in the eyes of the law ownership of the ETH never changed hands.

It gets a little complicated with cryptocurrencies in that they effectively setup a separate ownership structure enforced by cryptography and independent of the laws of any one nation. So the court may rule that the Ethereum never changed hands and so still belongs to the original owner - but the blockchain says otherwise, and good luck convincing 51% of miners (many of whom are not U.S. citizens) that they should mine a transaction just to resolve this one case.

[smsm42]

Courts know how to deal with cases where change of ownership (or another tort) is not reversible. It's as simple as if I promised you to pay you $100 for the dinner in your restaurant, ate the dinner and then never paid because I had no money. Obviously I was perpetuating fraud - I knew I have no money and still ate. But I can't return you the ownership of the food I ate. So the court would just assign just compensation (via various mechanisms) for fraud in that case, and maybe something on top to punish me for what I did. The only problem would be collecting it may prove impossible in this case.