New Hampshire is the only New England state that didn't join a coalition opposing the proposed rollback of the Clean Power Plan.
The EPA wants to replace the Obama-era plan with a rule that loosens carbon emissions standards for coal-fired power plants.
In a lengthy comment this week, the attorneys general of 26 states, cities and counties laid out their strong opposition.
They argue, in part, that the government has a legal responsibility to do more to combat climate change.
New Hampshire is one of the few East Coast states, and the only state in New England, that didn't sign on.
Officials with the state attorney general's office declined to comment as to why.
Gov. Chris Sununu's office and the New York attorney general's office, which spearheaded the coalition, did not immediately respond to a request for comment.
But it’s disappointing to Sara Pereschino, a New Hampshire organizer with the group Moms Clean Air Force.
“There's no state line that divides our air quality, so we all need to be in this together,” she says.
Absent state and federal action on the issue, she says groups like hers will focus on local organizing -- including encouraging towns to invest in renewable energy.