President Obama has just won two huge victories in the Supreme Court. But he should be wary of battles on other fronts. Opponents are grumbling about another Obama brainchild: climate change regulations.

Indiana Gov. Mike Pence sent a letter to Obama Wednesday stating that his state will not comply with the Environmental Protection Agency’s Clean Power Plan. The plan would require states to develop a plan to reduce carbon emissions from power plants. He argued that the proposal would increase costs of electricity, make the state’s electric service less reliable and slow economic growth.