The Liquor Con­trol Com­mis­sion­er shall have the right to exam­ine, or cause to be exam­ined, under oath, any appli­cant for a local license or for renew­al there­of, or any licensee upon whom notice of revo­ca­tion or sus­pen­sion has been served, and to exam­ine or cause to be exam­ined, the books and records of any such appli­cant or licensee; to hear tes­ti­mo­ny and take proof for his infor­ma­tion in the per­for­mance of his duties, includ­ing but not lim­it­ed to requir­ing the pro­duc­tion of an affi­davit affirm­ing any par­tic­u­lar or spe­cif­ic ques­tion posed by the Liquor Con­trol Com­mis­sion­er and for such pur­pose to issue sub­poe­nas which shall be effec­tive in any part of this State.  For the pur­pose of obtain­ing any of the infor­ma­tion desired by the Liquor Con­trol Com­mis­sion­er under this Sec­tion, the Liquor Con­trol Com­mis­sion­er may autho­rize its agent to act on its behalf.  (See 235 ILCS Sec. 5/4–5)