Twenty-two U.S. states and seven cities went to court last week, trying to block the Trump administration from rolling back Obama-era restrictions on coal-fired electricity under the Clean Power Plan.

“The court challenge, led by New York’s attorney general, Letitia James, argued that the Trump administration’s [Environmental Protection Agency] had no basis for weakening an Obama-era regulation that set the first ever national limits on carbon dioxide pollution from power plants,” the New York Times reports. Depending on how it is eventually decided, the case “could determine how much leverage the federal government has to fight climate change in the future.”

“The science is indisputable. Our climate is changing. Ice caps are melting,” James said.

“Without significant course correction, we are careening towards a climate disaster,” she added, vowing that the coalition of states and cities “will fight back against this unlawful, do-nothing rule.”

The U.S. Supreme Court previously blocked implementation of the Clean Power Plan in 2016, the Times recalls. Now, the challenge before the U.S. Court of Appeals “argues that the Trump administration’s replacement, known as the Affordable Clean Energy rule, ignores the EPA’s responsibility under the law to set limits on greenhouse gases. The lawsuit also says the new rule would actually extend the life of dirty and aging coal-burning plants, promoting an increase in pollution instead of curbing it.”

Unlike the Clean Power Plan, the Trump rule sets no cap on actual greenhouse gas emissions. “Instead, it leaves it up to states to decide whether, or if, to scale back emissions and pick from a menu of technologies to improve power plant efficiency at the facility level,” the Times notes. As well, pursuant to the EPA’s obligation under the Clean Air Act to use the “best systems of emissions reduction,” Obama’s CPP included a range of choices—from natural gas to solar and wind, from carbon pricing to carbon capture. The Trump plan “focuses solely on new efficiency measures for individual plants,” with EPA Administrator and former coal lobbyist Andrew Wheeler now arguing the Obama approach overreached the government’s authority.

California Attorney General Xavier Becerra called the “toothless” Trump rule a “fossil fuel protection plan” that artificially narrows the EPA’s authority. “The Clean Air Act requires the EPA to utilize the best system of emissions reduction that it can find,” he said. “This rule does the opposite.”

The jurisdictions joining New York and California in the suit include Colorado, Connecticut, Delaware, Hawaii, Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New Mexico, North Carolina, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia, Washington, Wisconsin, and the District of Columbia, as well as the cities of Boulder, Chicago, Los Angeles, New York, Philadelphia, and South Miami. The Times notes that Wisconsin, North Carolina, and Colorado were all parties to the previous challenge to the Clean Power Plan when their governors were Republicans.

“The blue-state coalition is getting bigger and the red-state coalition is getting smaller,” said David Doniger, senior strategic director of climate change policy at the Natural Resources Defense Council. The Times said NRDC, Sierra Club, and the U.S. Environmental Defense Fund were all expected to file their own legal challenges against the Trump rule, while the American Public Health Association and the American Lung Association had already done so.

But despite the wide lineup against the rule, the Times says James and her supporters may be playing with fire. “It is a case that could go all the way to the Supreme Court,” the paper notes. “If justices there were to ultimately decide in favour of the Trump administration, it could weaken the ability of future presidents to regulate carbon dioxide pollution from power plants, experts said, and make it  harder for the United States to tackle climate change.”

That outcome “would have a devastating effect on the ability of future administrations to regulate greenhouse gases under the Clean Air Act,” said New York University environmental law specialist Richard Revesz.