Blue sky law, any of various U.S. state laws designed to regulate sales practices associated with securities (e.g., stocks and bonds). The term blue sky law originated from concerns that fraudulent securities offerings were so brazen and commonplace that issuers would sell building lots in the blue sky.

Blue sky laws typically require the registration of any securities sold in a state, regulate broker-dealer and investment advisers, impose liability for false and misleading information relating to securities, and establish administrative agencies to enforce the laws. The registration requirements often include a merit review that gives the administrative agency the power to prohibit the sale of securities that it considers to be unfair or inequitable. This is in contrast to the federal securities-law approach, which relies on the market to determine a fair price after ensuring full disclosure of relevant information.

In general, blue sky laws predate the Securities Act of 1933 and the Securities Exchange Act of 1934 and were not preempted by those federal acts. By 1931 nearly all U.S. states had in place laws regulating the sales of securities. Blue sky laws in use in most U.S. states today are based on the Uniform Securities Act (USA) of 1956, which was designed by federal legislators to serve as a template states could use to craft their own laws. Although most states adopted some form of the USA, many made variations to it, which resulted in significant differences from state to state. Judicial interpretations of the USA can also vary significantly from state to state. Thus, actions that may be considered fraudulent under the USA in one state may not be considered fraudulent in a different state.

In an attempt to achieve greater uniformity between states, and thus reduce the burden on issuers and broker-dealers, the U.S. Congress passed the National Securities Markets Improvement Act (NSMIA) of 1996. The NSMIA classifies certain securities as covered securities, which are exempt from state registration and merit-review requirements. The covered securities include those listed on a national stock exchange and mutual funds. In 1998 Congress passed the Securities Litigation Uniform Standards Act (SLUSA) in order to place limits on state court jurisdiction over securities fraud lawsuits. Under the act, federal courts have exclusive jurisdiction over class actions alleging fraud.

The SLUSA does not prohibit state and local governments (and their pension funds) from bringing securities fraud claims. The importance of this exception became clear in 2002, when the New York attorney general used the state’s blue sky law (known as the Martin Act) to reach a settlement with Merrill Lynch that required the company to make significant changes to its operating and disclosure practices. This settlement became a leading example of regulation by prosecution. Other states subsequently amended their blue sky laws to increase the prosecutorial powers of their attorneys general. Congress also considered new legislation in an ongoing attempt to find the appropriate balance between federal and state powers in securities regulation.