Attorney General Cynthia Coffman is facing sharp questions from Democratic lawmakers about the costs and legal conflicts related to her decision to join a lawsuit to block the Obama administration’s tougher air quality standards.

Coffman, a Republican, brushed aside the concerns at a legislative hearing Thursday, defending her authority to challenge the Clean Power Plan emission rules.

Gov. John Hickenlooper disputes Coffman’s legal standing and recently asked the Colorado Supreme Court to intervene and declare that he “has ultimate authority” on whether to sue the federal government. The attorney general’s office will respond with a legal brief Friday.

The constitution, Coffman said, gives her “common law” authority to represent Colorado residents that goes beyond the limited powers outlined in state law.

“We represent the people of the state as independently elected officials,” Coffman told lawmakers. “The statute describes some of the specific clients, but that is not the only representation we provide, nor the only role of the attorney general.”

In the Joint Budget Committee hearing, Coffman acknowledged that taxpayers will pay the bill related to the lawsuit, but suggested the state’s share is “marginal” because the lead states — West Virginia and Texas — will incur “the vast majority of the cost of litigation.”

Colorado is one of roughly two dozen states challenging the new EPA regulations to cut carbon emissions from coal-burning power plants nationwide by 32 percent before 2030, compared to 2005 levels.

In an interview, Coffman said she didn’t know how much it would ultimately cost. Hickenlooper’s office hired Denver law firm Reilly Pozner to file the petition to the Supreme Court. It cost $5,000 and the contract caps legal fees at $25,000, according to the governor’s office.

At the same time Coffman challenges the law, attorneys in her office are working to help the state meet the emission targets. Since the start of the year, the state’s environmental agency paid the attorney general’s office $27,000 for 270 hours of legal work.

“Does it make you uncomfortable to be taking money from (the state) to help them implement a federal law that you are simultaneously attacking?” Sen. Pat Steadman, D-Denver asked Coffman.

“It doesn’t make me at all uncomfortable because that is the dual role of the attorney general of any state,” she responded. “We represent the state of Colorado and the people of Colorado. Sometimes that requires taking action that a specific client may disagree with.”

Rep. KC Becker, D-Boulder, asked “what “firewalls are in place” to prevent conflicts in this case.

“It depends on the particular situation,” Coffman responded, “but for the most part we don’t have firewalls between the front office and the attorneys representing the individual (agencies).”

The attorney general’s chief deputy interjected to argue there is no conflict, in part because the legal questions in each matter are different.

John Frank: 303-954-2409, jfrank@denverpost.com or @ByJohnFrank