DRM provides liability coverage to "any individual serving as a guardian or limited guardian for any consumer of a community services board or behavioral health authority or any patient or resident of a state facility operated by the Department of Behavioral Health and Developmental Services" ( § 2.2-1839, as amended). Participation in this plan is voluntary and must be approved by the executive director of the community services board or behavioral health authority or the Commissioner of the Department of Mental Health, Mental Retardation and Substance Abuse Services, as appropriate.