A federal appeals court panel on Tuesday struck down a 2018 Trump administration rule that had relieved states of their obligation to curb air pollution that causes smog in downwind states hundreds of miles away.

The ruling requires the Environmental Protection Agency to draw up a new plan for addressing the nation’s long-standing problems with ground-level ozone, or smog, to meet the requirements of the Clean Air Act. It’s a task that the Trump administration has made far more difficult by rolling back the restrictions on coal power plant pollution in the Clean Power Plan, the Obama administration’s signature policy on climate change.

The court’s decision extends the Trump administration’s losing record in defending its rollbacks of environmental regulations—this time, with the ruling coming from one of the president’s own judicial picks.

Judge Gregory Katsas, who served as a deputy White House counsel before President Donald Trump named him to the District of Columbia U.S. Circuit Court of Appeals in 2017, joined Judges Judith Rogers and Thomas Griffith in finding that the administration’s so-called “Close-Out Rule” was not permissible under the Clean Air Act. (Rogers was appointed by President Bill Clinton, and Griffith by President George W. Bush.)

The EPA finalized the “Close-Out Rule” last year, ending a requirement that upwind states reduce smog-forming pollution from coal power plants. The agency concluded it would not be feasible to put into place cost-effective measures, and it projected that all states would soon be in compliance with federal ozone standard without further federal action.

New York, Connecticut and New Jersey sued, arguing that they had areas with serious smog problems and would be unable to meet the federal ozone standard by the law’s 2021 deadline because of pollution that drifts over their borders from other states. The appeals court panel agreed with them, ruling that the Clean Air Act’s Good Neighbor Provision requires that upwind states eliminate significant contributions to other states’ pollution problems without regard to feasibility.

Richard Revesz, director of the Institute for Policy Integrity at New York University School of Law, who had filed a friend-of-the-court brief in support of the states, praised the ruling. “A core obligation of the EPA under the Clean Air Act is to protect the air quality of downwind states that suffer from excessive upwind pollution,” he said. “The Trump administration has consistently flouted this obligation.”

The ruling is closely connected to a decision by the same court two weeks ago in a separate case, in which an Obama administration rule that would have partially addressed upwind pollution was thrown out on the same legal basis for not going far enough.

The court on Tuesday noted that the EPA had indicated it might seek rehearings before the full court of appeals on both cases. Noting how little time was remaining for the downwind states to meet the 2021 ozone deadline, the court set an expedited schedule, with the Trump administration given only until Oct. 28 to file for rehearing of the cases.

Coal Power’s Smog Problem

Together, the two decisions require the EPA to go back to the drawing board to address a long-running problem for both Republican and Democratic administrations.

The genesis of much of the smog that troubles cities is pollution from coal-fired power plants and industrial smokestacks many miles away, combined with emissions from traffic on urban roadways.

Smog forms when two types of pollutants from fossil fuel burning—nitrogen oxides and volatile organic compounds—mix in a photochemical reaction. It can trigger chest pain, coughing, and airway inflammation. Long-term exposure can cause permanent lung damage or abnormal lung development in children. 

Although the Obama administration’s cross-state pollution rule only partially addressed the upwind pollution problem, it projected that its Clean Power Plan would result in significant reductions of smog-forming pollutants.

As a side benefit of cutting carbon emissions from coal power plants, the Obama EPA projected smog-forming nitrogen oxides would fall 22 percent by 2030 compared to the status quo without the rule in place. The Trump administration expects nitrogen oxide emissions to fall by only 0.9 percent by 2030 compared to the status quo. The Obama and Trump administrations have wildly different projections on pollution trends, though, making comparisons difficult. The bottom line is that the Trump administration sees pollution falling so quickly without regulation that no further controls are necessary.

Latest Court Loss for a Trump Rollback

Without a strong climate policy to reduce coal power pollution in place, the Trump administration has fewer options for addressing smog. Federal officials may have to look to regulation of other industrial sources of pollution if they are to meet the requirements of the law as articulated by the court.

Earthjustice, one of the environmental groups that joined in the case, said the decision will benefit more than 36 million people in the Eastern United States and Texas who live in counties that have ozone levels that exceed the federal standard.

“This win brings us one step closer to addressing the disproportionate, cumulative impacts borne by communities of color in the Houston nonattainment area every day,” said Juan Parras, executive director of Texas Environmental Justice Advocacy Services.

Out of more than 50 court rulings so far on agency policy under President Donald Trump, the government has lost 93 percent, according to tracking by the Institute for Policy Integrity at New York University School of Law.