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This summer, citing authority under the Clean Air Act, the EPA will put forth carbon emission limits for existing power plants. The fossil fuels industry, along with lawmakers from both parties, say that rule is potentially devastating for the American coal industry. Coal still accounts for nearly 40 percent of the nation’s electricity.

Specialists say the administration also is likely to propose limits on methane emissions from gas-drilling sites and other locations.

Last week, the EPA released regulations designed to make wood heaters burn up to 80 percent cleaner, part of an effort to crack down on soot pollution.

But those moves simply won’t amount to the kind of game-changer this administration is hoping for, and much of what can be accomplished through executive authority already has been done, said Jeffrey Holmstead, a partner at the Washington law firm Bracewell & Giuliani and assistant administrator of the EPA’s air and radiation office during the George W. Bush administration.

“There’s not a lot of low-hanging fruit left,” Mr. Holmstead said. “That’s a real challenge, and I think the White House is realizing there are limitations. Even on the EPA rules, and even though the president has established a very aggressive schedule, all of the heavy lifting will take place after he leaves office.”

Indeed, the highly touted fuel economy standards aren’t fully in place until 2025, theoretically giving Mr. Obama’s successors the ability to slow or alter the policy.

The implementation of the EPA’s power plant rules also will continue long after Mr. Obama leaves office. They also have become the targets of numerous lawsuits as the fossil fuels industry and others challenge the administration’s authority under the Clean Air Act to take such actions.

In the end, the courts could have the final say on how far Mr. Obama can go through executive action.

“The challenge is that by trying to do things with executive action, they’re pushing up against the fact that the statutes they want to use [such as the Clean Air Act] were not designed for that purpose,” Mr. Holmstead said.