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

A decision by the high court, with its conservative majority, could shred President Biden's plans to cut greenhouse emissions by half by the end of the decade.

The federal government's ability to affordably reduce greenhouse gases from power plants could be in danger. The power sector is the second largest source of carbon emissions in the United States.

The outcome could have repercussions that stretch well beyond air pollution, limiting 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, it could be devastating for other agencies. It could limit the Fed's authority to set interest rates.

There is a federal regulation that governs emissions from power plants. The regulation never took effect and is not currently in existence.

The Clean Power Plan was announced by President Barack Obama in 2015. The Clean Air Act gave the Obama administration the authority to require states to replace 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.

The Clean Power Plan was never implemented. The program was put on hold by the Supreme Court after a number of lawsuits. President Donald J. Trump instituted a new plan that was essentially the same as no regulation. On the last full day of Mr. Trump's presidency, a federal appeals court found that the administration had misinterpreted the law. The Biden administration has yet to issue its own regulation.

Legal experts said that it's unusual for the Supreme Court to take up a case about a hypothetical future regulation.

It is weird for the court to consider the authority of E.P.A. to regulate greenhouse gases when no regulation is being defended.

President Joe Biden spoke at the Flatirons campus of the National Renewable Energy Laboratory in 2021. Credit...Evan Vucci/Associated Press

The Obama Clean Power Plan was challenged in the high court by the West Virginia case.

Republican attorneys general in 18 states and some of the nation's largest coal companies will argue that the 1970 Clean Air Act limits the E.P.A. to dictate changes only at individual power plants.

Conservatives have long argued that the executive branch oversteps its authority in regulating economic activity.

Patrick Morrisey, the attorney general of West Virginia, spoke at an event in Washington earlier this month, ahead of his appearance before the Supreme Court. This case is all about that. It is very straightforward.

Congress delegated authority to the executive branch to regulate air pollution, according to others. They say that the executive implements the law through regulation.

The fact that the opponents are particularly shrill in their objection doesn't change the fact that the agencies have produced hundreds of regulation since the New Deal.

Each side has received legal backing from their supporters. Many of the nation's largest electric utilities have filed legal briefs in support of the government. They are joined by 192 members of Congress, the U.S. Conference of Mayors, climate and public health advocates and tech giants.

A group affiliated with the libertarian Koch family is one of the most powerful conservative groups in the country.

He said that he was encouraged by the 6-3 split on the court between conservatives and liberals.

Biden administration officials and environmentalists concede that the court has made decisions against federal rules, such as blocking a vaccine mandate and ending Mr. Biden's eviction moratorium.

David Doniger, a lawyer for the Natural Resources Defense Council, said that the court is not friendly to government action.

The spokesman for the Justice Department wouldn't discuss the case. The current absence of any federal greenhouse gas regulation causes them no tangible harm, as noted in the Biden administration's brief to the court.

The West Virginia case against the Obama power plant regulation was first heard by Justice Kavanaugh when he was a federal appeals judge.

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A world on fire. A United Nations report has concluded that the risk of devastating wildfires around the world could increase by up to 57 percent by the end of the century.

It is melting away. A new analysis of satellite images shows that the sea ice around Antarctica has reached a record low. Warming ocean temperatures may have played a role in the effect of climate change on sea ice.

The water supplies are being let down. Millions of people depend on glaciers for drinking water, crop irrigation and everyday use, and the world's glaciers may contain less water than previously thought.

The appeals court dismissed the case because the rule was only in draft form. The West Virginia lawyers were told by Mr. Kavanaugh that it was unusual to get in the middle of it.

Some of the nation's largest private and public power companies support a broad regulation of their greenhouse pollution.

The power companies prefer the flexibility offered by the Obama plan that would allow them to lower emissions by shutting down some plants, making others more efficient, and expanding wind and solar. They don't want to be required to make highly prescribed changes to individual power plants because they say it would drive up costs.

The regulated industry is saying that they are not fighting the authority of the EPA.

The people who are regulated are not complaining about the vaccine mandate, as was pointed out by Justice Kavanaugh.

Smokestacks at a coal power plant near Emmett, Kan., last year.Credit...Charlie Riedel/Associated Press

The lawyers for the E.P.A. are expected to propose a power plant climate regulation next month.

On the same day that the Supreme Court is hearing the case, the United Nations will release a report detailing the dire threats that global warming poses to human civilization.

In the past year alone, floods, fires, and rising seas have killed people and caused billions of dollars in damage across the United States, and Mr. Biden has pledged to aggressively cut greenhouse gases. The United States has pumped the most pollution into the atmosphere.

If Republicans win control of one or both houses of Congress this fall, Mr. Biden's climate legislation could collapse.

The power, authority and reach of regulations have been placed more emphasis. Next year, the E.P.A. will announce tough new limits on auto pollution in order to speed up the shift from gasoline-powered cars to electric vehicles.

Even though the details of the coming rules are not yet known, the case is not premature.

The attorney general of West Virginia said that the threat was real.

Legal experts on both sides agree that it is the first of many cases that will address the growing authority of federal agencies at a time when Congress has failed to pass new laws on issues such as climate change and gun control.

The professor at Case Western Reserve University said that Congress gets fancy pins and nice offices because they don't legislate. There is a bigger question of whether the courts should approve of that.