Madigan has filed a legislative resolution asking the Illinois Power Agency to determine whether to reverse part of a 1997 law and allow electric companies to run their own power-generating plants.
Under the law, Ameren Illinois and Commonwealth Edison stopped generating electricity and became power-delivery companies only. The power plants became separate, unregulated entities.
Ameren Illinois spokesman Leigh Morris said the utility has long believed the state should consider reintegration of power delivery and power generation.
However, Exelon Corp. spokeswoman Kathleen Cantillon said Exelon expects any study to determine competitive markets are the best value for Illinois consumers.