Investopedia Says
Investopedia explains 'Naked Shorting'
Naked shorting is illegal because it allows manipulators a chance to force stock prices down without regard for normal stock supply/demand patterns.
In 2007, the Securities and Exchange Commission (SEC) amended Regulation SHO to further limit possibilities for naked shorting by removing loopholes that existed for some broker/dealers. Regulation SHO requires lists to be published that track stocks with unusually high trends in "fail to deliver" shares. Some analysts point to the fact that naked shorting, albeit inadvertently, may help markets stay in balance by allowing the negative sentiment to be reflected in certain stocks' prices.