If you are the owner of a building or property that allows public access in the state of Illinois, and do not wish firearms to be allowed on the premises, you must comply to Illinois' gun sign laws pursuant to 430 ILCS 66/65.
430 ILCS 66/65 Prohibited areas. (d) Signs stating that the carrying of firearms is prohibited shall be clearly and conspicuously posted at the entrance of a building, premises, or real property specified in this Section as a prohibited area, unless the building or premises is a private residence. Signs shall be of a uniform design as established by the Department and shall be 4 inches by 6 inches in size. The Department shall adopt rules for standardized signs to be used under this subsection.
