The primary control over an agency is the enabling legislation that the legislature passes to establish the agency. Some enabling legislation is very general. It is not unusual to see state public health laws, at least older ones, say only that the public health department should protect the public’s health in whatever ways are appropriate. This is sufficient for civil enforcement, although it would probably be seen as too vague to support criminal prosecution. Congress seldom passes any simple laws, but there is still great variation in the detail in the legislation for various agency functions and civil law enforcement. In some cases, the law sets out the policy that Congress wants implemented and the basic nature of the enforcement mechanisms, and the agency is given the power to flesh out the details with administrative rules. At least theoretically, Congress leaves more details to the agency when the regulated matter involves scientific or technical decision making. An example would be the decisions on research funding by the National Institutes of Health (NIH). NIH is generally allowed broad discretion to distribute research funds based on peer reviewed grant proposals. In some cases, however, influential congresspersons get laws bypassing NIH review and giving research money directly to institutions in their states.

The Americans with Disabilities Act is an example of a very specific, detailed law that leaves the agency little latitude for regulatory discretion. Many provisions of this law were very controversial and the final statute represents detailed compromises worked out between various interest groups. Little was left to the agencies to flesh out because businesses and others needed certain and consistent interpretation of the law if they were to make fundamental changes in the way they dealt with persons with disabilities. The details of enforcement and ambiguities in the law have to be worked out by the courts, rather than by the agency, resulting in a high volume of litigation.