An administrative agency may exercise only the powers given by the law that creates it, that is, its enabling legislation. Some enabling legislation, such as the tax code, is very detailed, running thousands of pages in length. This reflects the congressional desire to exercise close control over the agency.

The enabling legislation for health departments was traditionally a general grant of authority to protect the public health and safety, with little specific legislative guidance. The details were left to the public health officers because there was little disagreement in society over the goals and methods of public health practice. As public health departments were given broader responsibilities, however, their enabling legislation grew more complicated, and their freedom of action was increasingly constrained. In several states, legislatures have greatly limited the traditional constitutional powers of health departments.