Administrative law in the United States during the last half century has been dominated by three major themes: (1) the extent to which legislative authority may be delegated to administrative agencies, (2) judicial review of legislative action, and (3) analysis of the formal aspects of agency procedures. At the core of this traditional approach to administrative law—defining its purpose—is the problem of the legitimacy of public administration. Specifically, the issue, to traditionalists, is how far administrative agencies can go before they impinge on the rights of private citizens.