Under his leadership, the SEC on September 17 and 18, 2008, imposed a variety of both permanent and emergency restrictions on short selling in response to the liquidity crisis. Abusive naked short selling, in which the seller intentionally fails to deliver the shares sold short in time for settlement, was banned outright, an exception for options market makers that had been in place for several years was eliminated, and a new anti-fraud provision, Rule 10b-21, was adopted to give specific enforcement authority in such cases. In September 2008, short selling of 799 financial stocks was temporarily curtailed in response to rumors accompanied by heightened short selling activity in the shares of major financial institutions.