The Chicago City Council on Friday approved what city officials say is the strictest handgun ordinance in the United States. The 45-to-0 vote came four days after a Supreme Court ruling made it almost certain that the city’s existing ban on handguns would be overturned. The court ruled that Americans have a right to own a gun for self-defense. The new ordinance bans gun stores in Chicago and prohibits gun owners from stepping outside their homes, even onto their porches, with a handgun. It will take effect in 10 days.