In the escalating battle over whether Herbalife is a legitimate business or a scam, the embattled company has found a vigorous champion in billionaire Carl Icahn, the activist investor who revealed in a securities filing earlier this month that he has taken a 13 percent stake in the vitamin and supplement maker. On Friday, Icahn continued his offensive against Herbalife’s detractors, taking aim at Sullivan & Cromwell in the process.

Appearing on CNBC’s Fast Money: Halftime Report, Carl Icahn repeatedly challenged S&C—which is among the law firms representing hedge fund titan William Ackman in his campaign to wipe out a company he claims is a pyramid scheme—to say publicly whether it shares the Pershing Square Capital Management CEO’s opinion that the vitamin and supplement maker is an elaborately constructed fraud.