The U.S. Securities and Exchange Commission (SEC) alleged crypto exchange Gemini and crypto lender Genesis Global Capital sold unregistered securities in a lawsuit filed late Thursday.

The investment regulator took aim at Gemini Earn, the troubled yield-bearing product that hundreds of thousands of U.S. investors entrusted with their crypto. Gemini generated yield on billions of dollars in crypto by loaning deposits to Genesis, which loaned them out again.

But Genesis’ November closing of lending withdrawals left some 340,000 Gemini Earn customers and about $900 million in crypto in limbo, the SEC said. (Genesis is owned by Digital Currency Group, which also owns CoinDesk). The regulator accused the popular program of being an unregistered security.

“Defendants offered and sold the Gemini Earn Agreements through the Gemini Earn Program without registering” with securities regulators, the complaint said. “As a result, investors lacked material information about the Gemini Earn program that would have been relevant to their investment decisions.”

The lawsuit is the latest twist in a high-stakes CEO battle pitting the Winklevoss twins of Gemini against Barry Silbert, head of DCG. The Winklevoss twins, shaken by the fall of their popular yield product, have accused Silbert of fraud in his company’s management of Genesis; Silbert calls the brothers' accusations a publicity stunt.

The lawsuit is a "manufactured parking ticket," said Gemini co-founder Tyler Winklevoss, responding in a Twitter thread. He noted that his company had been in discussions with the SEC over the Earn product for nearly 17 months and the agency "never raised the prospect of any enforcement action until AFTER Genesis paused withdrawals on November 16th."

Read more: DCG's Barry Silbert Talks About Genesis in Letter to Shareholders

UPDATE (Jan. 13, 2023 13:00 UTC): Adds Tyler Winklevoss' comments.