Forbes cites Vice President for Policy and Senior Fellow Wayne Crews on regulatory dark matter:
These actions are the latest attempt to ensure that the guidance agencies provide regulated parties is informative without being binding, or legally enforceable. Agency guidance, or “regulatory dark matter” as Forbes contributor Wayne Crews has dubbed it, can refer to a variety of different policy statements and interpretive rules, including manuals, opinion letters, and even blog posts. They can provide valuable information on how an agency interprets regulations and statutory law, providing a safe harbor on which regulated parties can rely. But there has long been concern that agencies sometimes use guidance inappropriately to make binding policy without going through transparent rulemaking steps.