The State of Illinois established guidelines regarding the wearing of face masks.  The IL Department of Commerce and Economic Opportunity released a revision to its Restore Illinois Safety Guidelines for Bar and Restaurant Establishments at the time which reflect the face mask guidance. 

Patrons should wear face coverings over their nose and mouth when approached and serviced by employees, including but not limited to when employees take patron orders, deliver food and beverages, and service tables, whether dining indoor or outdoor. 

The guidelines can be found here face mask guidelines