Riverstone Consultancy Inc., based in Houston, Texas, has filed a lawsuit against Tether, alleging the company unlawfully froze approximately $44 million in USDT at the request of Bulgarian local police. The lawsuit claims Tether did not follow proper international asset freezing procedures, resulting in Riverstone missing several investment opportunities. Riverstone is seeking a court order for Tether to release the funds and compensate for damages. However, blockchain analysts suggest the funds may be linked to multiple Ponzi schemes.