In a significant decision that reinforces transparency rules for local governments, the Illinois Appellate Court has barred larger municipalities in the state from leveraging special powers granted them under the Illinois Constitution to end-run open-records law.

The decision, coming in a case brought by the Better Government Association against the suburb of Rosemont, makes clear that municipalities are not free to make their own rules about what they are legally bound to disclose under the state Freedom of Information Act.

“Only state statutes may create additional restrictions on disclosure of information,” the court wrote in its ruling, which affirmed a lower court decision invalidating a village ordinance that sought to carve out Rosemont-specific exceptions to open records law that allowed it to keep secret information about certain financial transactions.

The principle upheld by the Appellate court has the power to extend beyond Rosemont and apply to all 214 so-called home-rule units in Illinois, the largest of which is Chicago. The state Constitution grants greater latitude in governing to home-rule municipalities, including the power to regulate public health issues, safety and welfare.

All Illinois communities with populations over 25,000 are automatically granted home-rule status, while some smaller towns also have achieved it through voter referendum.

The BGA filed its suit in 2015 after Rosemont refused to release financial and revenue figures in some contracts. The village argued that a recently passed ordinance protected the information from disclosure, with Rosemont mayor Bradley Stephens describing it as “trade secrets.”

The BGA’s suit came after Rosemont had held back similar information sought by the Chicago Tribune for contracts the village signed with country superstar Garth Brooks’ longtime promoter for Brooks to hold a series of concerts at the village-owned Allstate Arena in 2014. Rosemont eventually did release more information in that case and disclosed it had paid Brooks $1 million to open his tour in the town located on the edge of O’Hare International Airport.

In its decision, the Appellate Court concluded that Rosemont’s attempt at legislating exceptions to open records law was a direct assault on transparency.

By Rosemont’s logic, the court said, “The public disclosure of information in the possession of a (home rule unit) would be largely at the unfettered discretion of that body. This would derogate the purpose of both the state and federal Freedom of Information Acts.”