The Clean Power Plan will have its day in court on Tuesday as oral arguments over the Obama administration's signature environmental regulation began in a Washington, D.C. courtroom.

The regulation would set carbon emission reduction goals from existing coal power plants for each state, leaving it up to them on how to reach those goals. The rule aims to reduce carbon pollution from the power sector by 30 percent by 2030.

Oral arguments began in the D.C. Court of Appeals with a line out the door and a former congressman, Republican Ed Whitfield of Kentucky, in attendance. There were no protesters.

Related Story:

The U.S. Chamber of Commerce is leading the challenge against the Environmental Protection Agency's regulation, with more than 160 other trade associations chipping in. President and CEO Thomas Donohue said that the regulations are unlawful and the case will bear that out.

"Not only are these regulations unlawful, they're also a bad deal for America," he said. "The rule will drive up electricity costs for businesses, consumers and families, impose tens of billions in annual compliance costs, and reduce our nation's global competitiveness — without any significant reduction in global greenhouse gas emissions.

"We look forward to presenting our legal arguments today, urging the court to invalidate a regulation that exceeds EPA's authority and will cause significant economic harm to the American people."

The EPA has the backing of environmentalists and Democratic attorneys general, and the administration has been firm in its belief that the rule is firmly grounded in the Clean Air Act.

Joanne Spalding, chief general counsel for the Sierra Club, said the environmentalist case will not only emphasize the health benefits of the regulation, but how it could benefit the economy.

"Today, the D.C. Circuit Court will hear not just how the Clean Power Plan saves lives and creates jobs, but how it is built on a strong, solid legal foundation," she said. "We are confident the Clean Power Plan's flexible, cost-effective approach to protect the health of our communities and tackle the climate crisis will be upheld."