Having practically banned the construction of new coal-fired power plants, Environmental Protection Agency regulators may try to cap emissions at existing coal plants, according to the acting head of the agency.

“[T]hat’s certainly something that will be on the table in this next fiscal year,” acting EPA Administrator Bob Perciasepe told reporters last week, per Midwest Energy News, after saying that the EPA intends to start “working with states on existing sources, but we’re not there yet.”

The EPA has already finalized New Source Performance standards, a regulation that limits how much carbon dioxide a new power plant may emit. Natural gas plants meet the standard, but coal plants emit more carbon dioxide than is allowed.

“Such a requirement is unprecedented under the Clean Air Act and will have the unfortunate effect of preventing the construction of new coal plants or the upgrading of existing sources,” wrote Sen. Joe Manchin, D-W.Va., Sen. Joe Donnelly, D-Ind., and Sen. Mary Landrieu, D-La., in a letter last month asking President Obama to reconsider the rule.

The EPA has already revealed that it designed that rule to be “painful” for coal communities. EPA New England regional administrator Curt Spaulding explained the rule last year. “Just two days ago, the decision on greenhouse gas performance standards, and saying basically, ‘gas plants are the performance standard, which means that if you want to build a coal plant you’ve got a big problem.’ That was a huge decision,” Spaulding said at a Yale forum. “You can’t imagine how tough that was, because — you got to remember — if you go to West Virginia, Pennsylvania, and all those places, you have coal communities who depend on coal,” he continued. “And to say, ‘We just think those communities should just go away’ — we can’t do that. But she had to do what the law and policy suggested and it’s painful. It is painful every step of the way.”

The Natural Resources Defense Council released a report pushing for the EPA to cap emissions from existing coal plants, using its authority under a 2007 Supreme Court ruling.

“The EPA would set different overall emissions goals for each state, depending on each state’s existing energy mix. Coal-heavy Indiana would have a different target than renewable-rich Iowa,” The Washington Post’s Brad Plumer explained. “At that point, regulators and utilities in each state could figure out for themselves how best to meet the targets.”