For ETH they can sue Vitalik Buterin, the rest of the Ethereum Co-Founders, and the Ethereum foundation. They are the issuers and majority of the ETH supply is there since the beginning.
Again, I don't know anything about the creators of ETH, but they may have a better defense of their actions then-- say -- Sam Bankman Freid.
They crowdfunded $18M and used that to develop and issue tokens. It was clearly under their control at the time.