An administrative agency can be created by constitution; by statute; by agency action and by executive order[i]. Administrative agencies are found at both the federal and state levels. The Federal Administrative Procedure Act (APA) and State Administrative Procedure Act are the statutes regulating administrative agencies in the federal and state level respectively.
Administrative agencies are not regarded as judicial systems or tribunals. An administrative agency has no general judicial powers. Whether an entity is a state agency is determined on the level of state control over that agency
Generally, administrative agencies do not belong to either executive or legislative branches. However, certain administrative agencies are considered as the agents of the legislative branch and executive branch depending upon the case.
An independent agency is an agency which is independent of the executive branch. However, these independent agencies cannot ignore or reject positions espoused by the President in order to make an informed decision on matters of national interest[ii]
[i] Bruggeman v. South Dakota Chem. Dependency Counselor Certification Bd., 1997 SD 132 (S.D. 1997)
[ii] Westinghouse Electric Corp. v. United States Nuclear Regulatory Com., 598 F.2d 759 (3d Cir. 1979)