Mo. Rev. Stat. § 354.559
No community-based health maintenance organization shall prohibit or restrict any provider from disclosing to any subscriber, enrollee or member any information that such provider deems appropriate regarding the nature of treatment, risks or alternatives thereto, the availability of other therapy, consultation or test, the decision of any plan to authorize or deny services, or to process the plan or any person to authorize or deny services, or to process the plan or any person contracting with the plan uses or proposes to use, to authorize or deny health care services or benefits. Any such prohibition or restriction contained in a contract with a provider entered into after August 28, 1997, shall be void and unenforceable. The standards used to determine if a community-based health maintenance organization has prohibited or restricted a provider's disclosure in violation of this section shall be those established by federal regulation of the Health Care Financing Administration for use in regulating managed care plans serving Medicare enrollees.
§ 354.559, RSMo