215 ILCS 165/7
Every physician licensed in Illinois to practice medicine in all of its branches, every podiatric physician licensed to practice podiatric medicine in Illinois, and every dentist and dental surgeon licensed to practice in Illinois may be eligible to render medical, podiatric or dental services respectively, upon such terms and conditions as may be mutually acceptable to such physician, podiatric physician , dentist or dental surgeon and to the health services plan corporation involved. Such a corporation shall impose no restrictions on the physicians, podiatric physicians , dentists or dental surgeons who treat its subscribers as to methods of diagnosis or treatment. The private physician-patient relationship shall be maintained, and subscribers shall at all times have free choice of any physician, podiatric physician , dentist or dental surgeon who is rendering service on behalf of the corporation. All of the records, charts, files and other data of a health services plan corporation pertaining to the condition of health of its subscribers and beneficiaries shall be and remain confidential, and no disclosure of the contents thereof shall be made by the corporation to any person, except upon the prior written authorization of the particular subscriber or beneficiary concerned.
215 ILCS 165/7