The state's high court is slated to hear oral arguments on the city of Chicago's pension reform appeal on November 17.
A Cook County Judge deemed Chicago's 2014 overhaul of its Municipal and Laborers pension funds unconstitutional in July, and the city has appealed the lower court ruling to the Illinois Supreme Court.
Under the Chicago pension measure, city workers had to pay more into their pension funds and cost-of-living increases were reduced for retirees. The city was required to pay more into the plans.
The Cook County judge's ruling against Chicago's pension measure was guided by a May decision from the Illinois Supreme Court involving a state pension reform law.
The court struck down the state pension measure on the grounds that it violated the Illinois Constitution's pension clause, which states that contractual pension benefits cannot be reduced.