The Security Act of 1933 deals with the registration of securities and led to the embargo of publicity materials during the time a company files a registration statement with the SEC for a public offering of securities (stock and bond offerings, for example) and the time the SEC declares it effective, which is the time when the company can actually offer the securities for sale. Publicity materials could be perceived as 'front-running' the offering and drive up the stock price. This period of time where publicity materials are embargoed is known as:

Preparing for Public Relations Certification.