Final answer:
The SEC has the regulatory authority over accounting principles for public corporations, reinforced by the Sarbanes-Oxley Act to protect investors.
Step-by-step explanation:
The group with regulatory authority over accounting principles used by public corporations in the United States is the Securities and Exchange Commission (SEC). The SEC enforces accounting standards that increase confidence in financial information provided by public corporations, protecting investors from accounting fraud. This regulatory framework was further strengthened with the enactment of the Sarbanes-Oxley Act in 2002, following major accounting scandals involving companies such as Enron, Tyco International, and WorldCom.