Senator Mitch McConnell of Kentucky, the Republican majority leader, has started an unusual pre-emptive campaign against the rules, asking governors to refuse to comply. Attorneys general from more than a dozen states are preparing legal challenges against the plan. Experts estimate that as many as 25 states will join in a suit against the rules and that the disputes will end up before the Supreme Court.

Leading the legal charge are states like Wyoming and West Virginia with economies that depend heavily on coal mining or cheap coal-fired electricity. Emissions from coal-fired power plants are the nation’s single largest source of carbon pollution, and lawmakers who oppose the rules have denounced them as a “war on coal.”

“Once the E.P.A. finalizes this regulation, West Virginia will go to court, and we will challenge it,” Patrick Morrisey, the attorney general of West Virginia, said in an interview with a radio station in the state on Friday. “We think this regulation is terrible for the consumers of the state of West Virginia. It’s going to lead to reduced jobs, higher electricity rates, and really will put stress on the reliability of the power grid. The worst part of this proposal is that it’s flatly illegal under the Clean Air Act and the Constitution, and we intend to challenge it vigorously.”

Although Obama administration officials have repeatedly said states will have flexibility to design their own plans, the final rules are explicitly meant to encourage the use of interstate cap-and-trade systems, in which states place a cap on carbon pollution and then create a market for buying permits or credits to pollute. The idea is that forcing companies to pay to pollute will drive them to cleaner sources of energy.

Mr. Obama tried but failed to push through a cap-and-trade bill in his first term, and since then, the term has become politically toxic: Republicans have attacked the idea as “cap and tax.”

But if the climate change regulations withstand legal challenges, many states could still end up putting cap-and-trade systems into effect. Officials familiar with the final rules said that in many cases, the easiest and cheapest way for states to comply would be by adopting cap-and-trade systems.

The rules take into account the fact that some states may refuse to submit plans, and on Monday, the administration will also unveil a template for a plan to be imposed on such states. That plan will include the option of allowing a state to join an interstate cap-and-trade system.