The Administrative Procedure Act of 1946 (5 U.S.C. §§ 553 et seq.) requires federal agencies to follow a specific process when issuing legally binding rules: publish a notice of proposed rulemaking in the Federal Register, allow at least 30 days for public comment, consider those comments, and then publish a final rule with a written explanation. Rules made without following this process are subject to judicial invalidation. The APA's notice-and-comment requirement is a core mechanism for democratic accountability in the regulatory process — it ensures that affected parties can participate before rules take effect. Informal agency memoranda and guidance documents are not legally binding rules and generally don't require notice-and-comment, but agencies can't use them to impose mandatory requirements that only formal rules can impose.