Private, self-regulatory organization overseen by the US Securities & Exchange Commission.

http://www.finra.org/

FINRA is the largest independent regulator for all securities firms doing business in the United States. Its chief role is to protect investors by maintaining the fairness of the US capital markets. FINRA, is a private corporation that acts as a self-regulatory organization (SRO).FINRA was formed by a consolidation of the enforcement arm of the New York Stock Exchange and the National Association of Securities Dealers.

FINRA regulates trading in equities, corporate bonds, securities futures, and options. FINRA oversees nearly 4,450 brokerage firms, about 161,065 branch offices and approximately 629,755 registered securities representatives. FINRA licenses individuals and admits firms to the industry, writes rules to govern their behavior, examines them for regulatory compliance, and is sanctioned by the U.S. Securities and Exchange Commission (SEC) to discipline registered representatives and member firms that fail to comply with federal securities laws and FINRA's rules and regulations.

FINRA Rules and Regulations

All firms dealing in securities that are not regulated by another SRO, such as by the Municipal Securities Rulemaking Board (MSRB)

http://en.wikipedia.org/wiki/Financial_Industry_Regulatory_Authority