Section (b)(3)(iii) of the Chicago Firearm Ordinance does not provide a person of ordinary intelligence a reasonable opportunity to know what is prohibited, in that it does not define the term "unlawful use of a weapon..." A person of ordinary intelligence would understand or interpret the term "unlawful use of a weapon that is a firearm" to mean using a firearm for an unlawful purpose, and not mere unlawful possession. ... There is something incongruent about a nonviolent person, who is not a felon but who is convicted of a misdemeanor offense of simple possession of a firearm, being forever barred from exercising his constitutional right to defend himself in his own home in Chicago against felons or violent criminals.

Chicago lawmakers have struggled to limit firearm possession in the city without violating the Constitution. The Chicago City Council unanimously approved [JURIST report] the Chicago Firearm Ordinance in July 2010, imposing strict regulations on firearm possession. Under the ordinance, residents who possess firearms are required to keep them inside their homes, and are not permitted to take their guns into the yard, garage or porch of the home. The legislation was enacted four days after the US Supreme Court ruled in McDonald v. Chicago [Cornell LII backgrounder; JURIST report] that the Second Amendment right to bear arms is applicable to the states as well as the federal government. The decision effectively struck down Chicago's former handgun ban, as it prohibited citizens from keeping handguns in their homes under any circumstances. The court's ruling in McDonald cited the holding in District of Columbia v. Heller [JURIST report] where the court held that the Second Amendment protects the right to possess a handgun in the home for the purpose of self-defense.