There are two types of rules: legislative and interpretive. Legislative rules can be further divided into those that are procedural and those that are substantive. As a general proposition, a legislative delegation of authority carries with it an implicit authority to establish procedures necessary to enforce and implement the agency’s delegated mandate.

Agencies are normally bound by their own procedural rules, as are those who deal with those agencies. The other form of rule is substantive. These rules affect the rights of individuals and are the functional equivalent of statutes. There is no inherent authority to promulgate substantive rules. Congress must delegate this authority. The Supreme Court has found, however, that the authority may be implicit in the agency’s man-date from Congress.

That is, the authority may be found in the absence of a statute expressly granting it as long as it is clear that Congress intended for the agency to have the authority to “fill in the gaps.” If promulgated properly, such rules have the effect of statutes; they require or prohibit actions and may impose penalties for violations of their mandates. Although a rule must be consistent with the agency’s enabling statute, it may declare something that the statute has not. The APA uses the phrase “substantive rules” rather than legislative rules.

A Court may not substitute its judgment for that of a substantive agency rule. That is, a reviewing Court cannot declare that a better standard or procedure must be used. A substantive rule has the force and effect of law. Interpretive rules do not declare something new; they do not fill in the gaps of legislation.