The Environmental Protection Agency said Monday that it would repeal some carbon dioxide emission rules for power plants, part of a broader effort to curtail the agency's role in regulating climate change.

The move would unwind two key policies of the Obama and Biden eras around carbon emissions.

The first would reverse Biden-era policies to crack down on pollution from coal plants and newly built natural-gas-fired power plants. The other concerns the EPA's broader authority to regulate climate pollution under the Clean Air Act, which could prevent future administrations from regulating power-plant emissions.

EPA Administrator Lee Zeldin called Monday's actions "the largest deregulatory action for the United States power sector in American history."

The agency acted in February to rescind the Obama-era endangerment finding, which classifies six greenhouse gases as a threat to public health and welfare.

That finding had provided the legal underpinning to climate rules that limited emissions from power plants and tightened fuel-economy standards for vehicles under the Clean Air Act. But the administration's rule changes earlier this year focused on the autos sector and tailpipe emissions, not the power industry.

"Today's proposal states the Clean Air Act does not give us the authority to regulate power-plant emissions based on climate change," Zeldin said at a G-20 Ministerial Meeting on Energy Abundance in Houston. "At EPA, we follow a very simple principle. If Congress didn't authorize it, EPA shouldn't be doing it."

A legal fight is already under way and is expected to grow.

The power industry had pushed back against Biden administration rules that would have required power plants to implement carbon capture and storage technology, or switch to hydrogen fuel from natural gas. New plants that didn't comply with one of those options wouldn't have been able to operate at full capacity.

The rules didn't apply to existing gas plants, the backbone of the nation's power supply. But many new gas-fired power plants are now proposed to meet surging demand for electricity for AI data centers.

The rule was considered especially difficult for coal-fired power plants, as they are already more complex and costly to operate than natural-gas plants, and have had a hard time competing in the market against gas and renewables.

Jim Matheson, chief executive of the National Rural Electric Cooperative Association, called the Biden-era rule "unachievable."

"It also exacerbates the pressures facing America's electric grid by forcing critical existing power plants into early retirement and severely restricting the operation of new natural gas plants," Matheson said.

Attorney Alex Bond of Baker Botts, who previously worked at the EPA office of general counsel, said there are several legal cases at play around the Clean Air Act, the endangerment finding and the EPA's climate authority.

"Ultimately this has the 'Supreme Court' written all over it," Bond said. "The question is just what issue is going to go up to the Supreme Court, and when are we going to get

any type resolution on what that authority looks like?"

The move to unwind EPA regulations has been seen as a victory for the fossil-fuel industry, which for years has pushed back against federal climate regulations. Since taking office, President Trump has framed fossil fuels as vital to economic and national security, and he has argued that increased reliance on them would help lower energy prices.

His administration has ordered several older fossil-fuel-fired power plants that were scheduled for retirement to continue operating under emergency orders. Last week, though, a federal appeals court struck down one of those orders to keep a coal-fired power plant in Michigan running past its planned retirement.