"Mr. Presnell asked during our meeting for an example of participation by a intervenor on a non-party basis," Case wrote, adding that he looked forward to speaking with them.

On July 3, a transcript shows Cooper went before Wake County Judge Paul Ridgeway and argued that the citizens groups should be excluded from the legal proceedings.

"They tried to keep us from being full parties in the case," said Frank Holleman, a senior attorney for the law center. "Duke is the lawbreaker. DENR is the law enforcement agency. They are supposed to be protecting the people. Instead, they are working with the lawbreaker to find a way to limit the participation of the citizens groups in the law enforcement proceedings in the way that will benefit the lawbreaker. It's astonishing."

The agency ultimately used its authority to intervene in the lawsuit, quickly negotiating a proposal where the $50 billion company would pay a $99,100 fine to settle environmental violations but be under no requirement to actually clean up its pollution.

Environmentalists have derided the proposal as a "sweetheart deal" by compliant state regulators to shield Duke from far harsher and more expensive penalties the company would have likely faced had the citizens groups been allowed move forward in federal court.