GS 150B-18 requires rules to be adopted in substantial compliance with Article 2A (rules). Prohibits agencies from implementing or enforcing against any person a policy, guideline, or other interpretive statement that meets the definition of a rule if the policy, guideline, or other interpretive statement has not been adopted as a rule in accordance with Article 2A. Amends GS 150B-18 by adding that any policy, guideline, or other interpretive statement that an agency attempts to implement or enforce inconsistent with this statute is unenforceable unless it is adopted as a rule in accordance with Article 2A.