The uptick rule refers to a trading restriction that disallowed short selling of securities except on an uptick. For the rule to be satisfied, the short must be either at a price above the last traded price of the security, or at the last traded price if that price was higher than the price in the previous trade. The U.S. Securities and Exchange Commission (SEC) defined the rule, and summarized it: "Rule 10a-1(a)(1) provided that, subject to certain exceptions, a listed security may be sold short (A) at a price above the price at which the immediately preceding sale was effected (plus tick), or (B) at the last sale price if it is higher than the last different price (zero-plus tick). Short sales were not permitted on minus ticks or zero-minus ticks, subject to narrow exceptions."The rule went into effect in 1938 and was removed when Rule 201 Regulation SHO became effective in 2007. In 2009, the reintroduction of the uptick rule was widely debated, and proposals for a form of its reintroduction by the SEC went into a public comment period on 2009-04-08. A modified form of the rule was adopted on 2010-02-24.