215 ILCS 165/3
It shall be unlawful for any person, except a health services plan corporation, incorporated under this Act, to establish, maintain or operate a voluntary health services plan. This prohibition, however, shall not be construed as preventing a person from furnishing health services to his employees or from furnishing such medical services as are required under the workers' compensation laws and related legislation, when the employees are not charged for such services; nor shall it be construed to prohibit an insurance company, or other corporation or society, which is subject to the supervision of the Director from operating in accordance with the laws governing insurance companies or such corporations or societies; nor shall it be construed to prohibit the continued operation of any medical or health service plan in existence and functioning at the effective date of this Act.
215 ILCS 165/3