Supreme Court Will Hear Biggest Climate Change Case in a Decade

WASHINGTON — In the most important environmental case in more than a decade, the Supreme Court on Monday will hear arguments in a dispute that could restrict or even eliminate the Environmental Protection Agency’s authority to control the pollution that is heating the planet.

A decision by the high court, with its conservative supermajority, could shred President Biden’s plans to halve the nation’s greenhouse emissions by the end of the decade, which scientists have said is necessary to avert the most catastrophic impacts of climate change.

“They could handcuff the federal government’s ability to affordably reduce greenhouse gases from power plants,” said Michael Oppenheimer, a professor of geosciences and international affairs at Princeton University.

But the outcome could also have repercussions that stretch well beyond air pollution, restricting the ability of federal agencies to regulate health care, workplace safety, telecommunications, the financial sector and more.

“If the court were to require the E.P.A. to have very specific, narrow direction to address greenhouse gases, as a practical matter it could be devastating for other agencies’ abilities to enact rules that safeguard the public health and welfare of the nation,” said Richard Lazarus, a professor of environmental law at Harvard. “It would restrict the enactment of regulations under any host of federal statutes — OSHA, the Clean Water Act, hazardous waste regulation. In theory it even could limit the Fed’s authority to set interest rates.”

At issue is a federal regulation that broadly governs emissions from power plants. But in a curious twist, the regulation actually never took effect and does not currently exist.

The legal wrangling began in 2015 when President Barack Obama announced the Clean Power Plan, his chief strategy to fight climate change. Citing its authority under the Clean Air Act, the Obama administration planned to require each state to lower carbon dioxide emissions from the electricity sector — primarily by replacing coal-fired power plants with wind, solar and other clean sources. Electricity generation is the second largest source of greenhouse gas emissions in the United States, behind transportation.

But the Clean Power Plan was never implemented. After a barrage of lawsuits from Republican states and the coal industry, the Supreme Court put the program on hold. Once President Donald J. Trump took office, he instituted a new plan that was effectively the same as no regulation. But on the last full day of Mr. Trump’s presidency, a federal appeals court found that the Trump administration had “misconceived the law” and vacated the Trump plan. That cleared the way for the Biden administration to issue its own regulation, which it has yet to do.

It is highly unusual for the Supreme Court to take up a case that revolves around a hypothetical future regulation, legal experts said.

“Trying to figure out the contours of E.P.A.’s authority to regulate…