It is widely accepted that the powers of the federal government flow from the U.S. Constitution. Yet in practice, most federal power is exercised through administrative agencies, institutions not mentioned in the Constitution. Since the New Deal Era, administrative law—the seemingly disparate set of rules governing agency action that are found in statutes, judicial decisions, and executive directives—has accommodated the emergence of this fourth branch of government not contemplated by the Framers. Familiar principles, including the separation of powers, the rule of law, and individual liberties, permeate administrative law. But these principles cannot be expressly located in the U.S. Constitution. So what is their legal and theoretical foundation? And how are they found in administrative law?
This Article argues that administrative law provides an unwritten constitution governing federal administrative agencies. American administrative law is illuminated law through the lens of constitutional theory, and particularly principles of British constitutionalism. This Article shows that administrative law rules, though not formally entrenched, perform essential constitutional functions where the written Constitution has little or no application. These functions include constituting government agencies, determining institutional boundaries, establishing the government–citizen relationship, and protecting fundamental values.
This unwritten constitution theory provides a legal and theoretical foundation for ensuring that the administrative state operates consistently with constitutional principles. It also legitimates administrative common law and illuminates political obligations to respect constitutional principles in administrative law development and reform.