The ordinance was pushed through quickly by Mayor Richard Daley and the City Council after the U.S. Supreme Court last month. The top U.S. court ruled that Americans have the right to have guns in their homes for protection.
The ordinance permits residents of the third-largest U.S. city to have only one working gun at a time in their homes and prohibits them from stepping outside, even onto their porches or in their garages, with a handgun.
Following the lead of Washington, D.C., which enacted a strict ordinance after the Supreme Court struck down its gun ban two years ago, Chicago also requires prospective gun owners to take a class and receive firearms training.
Chicago's ordinance also bans gun shops from setting up shop in the city and bars anyone convicted of a violent crime, domestic violence or two or more convictions for driving under the influence of alcohol or drugs from owning a handgun.
Also starting Monday is a 90-day grace period in which residents who owned handguns illegally during the ban can register them without penalty.
Chicago's ordinance was widely criticized by gun rights advocates, who have said the city is simply trying to make it as difficult as it can for people to own guns and putting up unconstitutional roadblocks in their way. They promised lawsuits and last week, even before the ordinance went into effect, at least two lawsuits were filed challenging the constitutionality of the ordinance.
City officials have said they believe the lawsuit is constitutional and that the Supreme Court specifically ruled that local jurisdictions have the right to impose reasonable regulations and restrictions.