The Environmental Protection Agency’s ability to regulate carbon dioxide and other greenhouse-gas emissions was dealt a massive blow by the US Supreme Court today.

Coming less than a week after it overturned the landmark abortion case Roe v. Wade, the court’s decision in West Virginia v. EPA could have far-reaching results for US climate policy as the world continues to set new records for emissions that drive global climate change.  

What was the ruling?

The decision states that the EPA’s actions in a 2015 rule, which included caps on emissions from power plants, overstepped the agency’s authority.

“Capping carbon dioxide emissions at a level that will force a nationwide transition away from the use of coal to generate electricity may be a sensible ‘solution to the crisis of the day,’” the decision reads. “But it is not plausible that Congress gave EPA the authority to adopt on its own such a regulatory scheme.”

Only Congress has the power to make “a decision of such magnitude and consequence,” it continues. 

This decision is likely to have “broad implications,” says Deborah Sivas, an environmental law professor at Stanford University. The court is not only constraining what the EPA can do on climate policy going forward, she adds; this opinion “seems to be a major blow for agency deference,” meaning that other agencies could face limitations in the future as well.

The ruling, which is the latest in a string of bombshell cases from the court, fell largely along ideological lines. Chief Justice John Roberts authored the majority opinion, and he was joined by his fellow conservatives: Justices Samuel Alito, Amy Coney Barrett, Neil Gorsuch, Brett Kavanaugh, and Clarence Thomas. Justices Stephen Breyer, Elena Kagan, and Sonia Sotomayor dissented.

What is the decision all about?

The main question in the case was how much power the EPA should have to regulate carbon emissions and what it should be allowed to do to accomplish that job. That question was occcasioned by a 2015 EPA rule called the Clean Power Plan.

The Clean Power Plan targeted greenhouse-gas emissions from power plants, requiring each state to make a plan to cut emissions and submit it to the federal government.

Several states and private groups immediately challenged the Clean Power Plan when it was released, calling it an overreach on the part of the agency, and the Supreme Court put it on hold in 2016. After a repeal of the plan during Donald Trump’s presidency and some legal back-and-forth, a Washington, DC, district court ruled in January 2021 that the Clean Power Plan did fall within the EPA’s authority.

The Supreme Court case West Virginia v. EPA is a result of challenges to that district court decision. A handful of states, as well as several coal companies, argued that the EPA did not have the authority to regulate emissions the way it tried to do in the Clean Power Plan.

What were the arguments in the case?

The states argue that the EPA should only be allowed to regulate individual power plants, not to set industry-wide standards.

Second, they argue that because the EPA was instating rules that would have wide-reaching economic impacts, the agency was broadly overstepping what Congress gave it the power to do.

The Clean Air Act of 1970 gave the EPA authority to regulate pollution, and amendments in 1990 expanded the agency’s role. This authority has been interpreted to include greenhouse-gas emissions, as the Supreme Court found in a 2007 case.

The Biden administration argues that the court shouldn’t be looking at the effects of the Clean Power Plan at all, since in fact the plan never took effect. It contends that the court should wait until there are new rules released before it decides how the EPA should regulate emissions. 

But the justices sided with the complaining states, ruling that the EPA’s plan overstepped the agency’s authority.

The dissenting justices argue that the ruling strips the EPA’s authority to regulate pollution, including greenhouse gases, an authority they say was granted by the Clean Air Act. 

In the dissenting opinion, the justices described the potential harms of climate change, including flooding, heat waves, and natural disasters, saying: “Congress charged EPA with addressing those potentially catastrophic harms, including through regulation of fossil-fuel-fired power plants.

“Section 111 of the Clean Air Act directs EPA to regulate stationary sources of any substance that ‘causes, or contributes significantly to, air pollution’ and that ‘may reasonably be anticipated to endanger public health or welfare.’ Carbon dioxide and other greenhouse gases fit that description.”

What does this all mean?

The decision will limit the ability of agencies like the EPA to take action on climate without backing from Congress. 

The agency will still be able to take some actions in regulating emissions, including requiring new technologies at power plants. But more wide-reaching programs, like setting emissions caps to encourage a shift away from coal, might be constrained in the future. 

“It sends a signal to EPA that when they make future rules about greenhouse gasses in particular, that they're going to be highly constrained in what they can do,” says David Victor, a public policy professor at the University of California, San Diego.

The federal government will still be able to encourage emissions cuts through incentives like tax credits and public investment, Victor explains, but when it comes to enforcing binding rules on climate action, it could be even more limited in the future, leaving it to states to step in.

“This case adds to a darkening cloud of uncertainty about the capacity of the federal government to regulate pollution,” Victor says. 

That uncertainty will make it harder for the federal government to make promises to other countries and influence their actions on climate, he says, and it could potentially cool private investment. 

Some see this case as a call to action for Congress. “Broadly, this reinforces how important congressional action on climate policy is,” says Lindsey Walter, deputy director of climate and energy at Third Way, a public policy think tank.

But as the dissenting justices put it, the decision is a blow to the federal government’s ability to move on climate change: 

“Today, the Court strips the Environmental Protection Agency (EPA) of the power Congress gave it to respond to ‘the most pressing environmental challenge of our time.’” 

This story will be updated.