Chicago, Cook County, and the State itself are the target of a flurry of lawsuits seeking to overturn various gun control ordinances. From the Bellingham Herald:

In an unrelenting campaign to overturn restrictive handgun laws in Illinois, gun rights advocates have pummeled Chicago and the state with lawsuits that could keep them entangled in court battles for years.

At least nine separate lawsuits targeting Chicago, Cook County and Illinois are working their way through the courts, most of them backed by the National Rifle Association, which is pouring financial resources and political clout into efforts to loosen gun laws across the country.

Those two paragraphs at the start of the article (originally published in the Chicago Tribune) should give you the gist of the bias of the piece. Still, plenty of valuable info including (about half-way down) a list of all pending litigation.

Somewhat related: Lawsuit against Alameda County (California) ban on gun shows is heading to a 9th Circuit full hearing by all 11 justices.