Montana Schools Group Workers Compensation Risk Retention Program v. Dep't of Labor and Industry Employment Relations Division [06/16/95] 1995 MTWCC 48 The method used by the Department of Labor and Industry to assess fees against insurers and self-insurers to fund government costs of administering the Workers’ Compensation and Occupational Disease Acts amounts to a de facto agency rule. Where section 39-71-201, MCA (1991) has left significant regulatory details to agency discretion and that discretion could be exercised in different manners, each impacting segments of the public differently, the assessment methodology must be adopted by rule following statutory rulemaking requirements (Montana Administrative Procedures Act). Once a rule is adopted, school district self-insurance association is entitled to have its 1992 assessment recomputed and to receive either a refund or credit if appropriate.