The Federal Reserve said on Wednesday that it had approved a final rule to clarify the process the new U.S. risk council will follow when it begins designating nonbank financial firms for heightened oversight, Reuters reported. That  group of regulators known as the Financial Stability Oversight Council is responsible for determining which nonbank firms are so critical that their failure could threaten the financial system. Regulators have not yet designated nonbank firms as systemically important, although three firms are said to be in the final stages of consideration.