The bill signing Monday comes as the federal Environmental Protection Agency has proposed rules that would require Missouri to cut carbon dioxide emissions from power plants by more than one-fifth by 2030.
Missouri's electricity production relies heavily on coal-fired power plants, which release greenhouse gases that contribute to climate change.
The bill says state officials can develop carbon dioxide emission standards that are less stringent than federal guidelines.
Missouri legislators had passed the measure before the proposed federal regulations were released. They were concerned the U.S. guidelines could be costly to comply with for electric companies.