Fortunately for the home owner, there is this (though the home owner will have to deal with Mayor Daley’s moaning and groaning):
The Illinois Legislature addressed city gun bans after Hale DeMar shot a home invader in the Gun Free Zone of Wilmette, IL. This makes it nearly impossible for police to charge people violating the gun ban if the gun/s are discovered after a self-defense incident.
(720 ILCS 5/24-10)
Sec. 24-10. Municipal ordinance regulating firearms; affirmative defense to a violation. It is an affirmative defense to a violation of a municipal ordinance that prohibits, regulates, or restricts the private ownership of firearms if the individual who is charged with the violation used the firearm in an act of self-defense or defense of another as defined in Sections 7-1 and 7-2 of this Code when on his or her land or in his or her abode or fixed place of business.