Tether’s assistance in law enforcement investigations has become highly sought-after by agencies around the world struggling to address surging crypto crime. Like many of Tether’s ownership details, this remains unconfirmed by the company itself. If retained, the stake would now be worth more than $13 billion, going by Forbes’ valuation of Tether. Such a line usually means that someone controls a firm, according to Ann Lipton, a professor of law at the University of Colorado Boulder. According to a person with knowledge of the communications, Tether has not responded to the senators’ questions.