235 ILCS 5/4-5

The local liquor control commissioner shall have the right to examine, or cause to be examined, under oath, any applicant for a local license or for a renewal thereof, or any licensee upon whom notice of revocation or suspension has been served in the manner hereinafter provided, 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, 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 local liquor control commissioner under this section, he may authorize his agent to act on his behalf.