It comes from constitutional law, from statutory law, and perhaps most important, from what judges have said about the administrative process in appellate court decisions.
Administrative law can contribute useful skills to public administration practitioners.
I must warn you, however, that administrative law can be complicated and confusing. During this semester, we shall attempt to explore some of the reasons why this is so. This is NOT a course intended for law students or legal practitioners. Rather, it is intended for the public sector manager or supervisor who must often read, interpret, apply and sometimes even write the rules and regulations in our society that affect both government bureaucracies and the people they serve. Cann, Steven J., Administrative Law , 2nd ed., Sage Publications, 1998.