Touting the plan at a White House ceremony, Obama described his unprecedented carbon dioxide limits as the biggest step ever taken by the U.S. on climate change. On that point, at least, his opponents agreed. They denounced his proposal as egregious federal overreach that would send power prices surging, and vowed lawsuits and legislation to try to stop it. Sixteen states — including energy-producing states like Kentucky, Wyoming and North Dakota — will face stricter emissions limits than they did under Obama's previous proposal. Montana's requirement more than doubled, from a 21 percent cut in the earlier plan to a 47 percent cut in the final version.