The Administrative Procedure Act (APA) (1946) (mostly found in 5 U.S.C. §§ 551-559, 701-706) is the basic law that tells Federal agencies how they must operate when they issue rules or adjudicate cases. The law spells out the basic "rules of the game." Thus, the minimum steps that an agency must follow when it issues most rules are spelled out in the APA-publish a proposal, invite and consider comment, and issue a final rule 30 days before its effective date.

In addition to the procedural requirements established in the APA, an agency may be required to follow additional procedural requirements contained in other statutes. For example, a law that establishes an agency or a law that assigns an agency new functions may contain procedural requirements in addition to those spelled out in the APA. Also, an agency may have adopted additional procedural rules beyond those required by the APA or the agency's own statute. These rules will usually be found in the Code of Federal Regulations, but sometimes are written only in an agency's internal documents. These additional rules are binding on an agency if it has announced that it will follow them.

Most states now have enacted state APAs that prescribe procedures for state administrative agencies.