Tennessee Code Title 56. Insurance § 56-7-117

(a) No group medical benefit contract issued by an insurance company, a hospital service corporation, a hospital and medical service corporation, a medical service corporation, a health maintenance organization or a health care center, that provides coverage for prescription drugs, may require any person covered under the contract to obtain prescription drugs from a mail-order pharmacy in order to obtain benefits for the drugs, or to pay an additional fee or be subjected to any other penalty for failing to utilize any mail-order pharmacy designated by the insurance company or other issuing organization.

(b) The commissioner is authorized to promulgate regulations to implement and enforce this section.