But Congress has also created a fifth branch of government that few people know about. This fifth branch is composed of so-called self-regulatory organizations. The largest and most powerful fifth branch agency is the Financial Industry Regulatory Authority, a Delaware not-for-profit organization. >>> Originalism, the Administrative State, and the Clash of Political TheoriesFINRA is not the only fifth branch agency. The fifth branch also includes the National Futures Association, the Municipal Securities Rulemaking Board, and the regulatory functions of the various national securities exchanges and registered clearing agencies.