5 ILCS 430/25-20a
In addition to investigatory authority otherwise granted by law, the Attorney General shall have the authority to investigate violations of this Act pursuant to Section 25-50 or Section 25-51 of this Act after receipt of notice from the Legislative Ethics Commission or pursuant to Section 5-45. The Attorney General shall have the discretion to determine the appropriate means of investigation as permitted by law, including (i) the request of information relating to an investigation from any person when the Attorney General deems that information necessary in conducting an investigation; and (ii) the issuance of subpoenas to compel the attendance of witnesses for the purposes of sworn testimony and production of documents and other items for inspection and copying and the service of those subpoenas.
Nothing in this Section shall be construed as granting the Attorney General the authority to investigate alleged misconduct pursuant to notice received under Section 5-45, Section 25-50, or Section 25-51 of this Act, if the information contained in the notice indicates that the alleged misconduct was minor in nature. As used in this Section, misconduct that is "minor in nature" means misconduct that was a violation of office, agency, or department policy and not of this Act or any other civil or criminal law.
5 ILCS 430/25-20a