WASHINGTON — The Supreme Court's surprise decision Tuesday to halt the carrying out of President Barack Obama's climate change regulation could weaken or even imperil the international global warming accord reached with great ceremony in Paris less than two months ago, climate diplomats say.
The Paris Agreement, the first accord to commit every country to combat climate change, had as a cornerstone Obama's assurance that the United States would enact strong, legally sound policies to significantly cut carbon emissions. The U.S. is the largest historical greenhouse gas polluter, although its annual emissions have been overtaken by China's.
But in the capitals of India and China, the other two largest polluters, climate change policy experts said the court's decision threw the United States' commitment into question, and possibly New Delhi's and Beijing's.
"If the U.S. Supreme Court actually declares the coal power plant rules stillborn, the chances of nurturing trust between countries would all but vanish," said Navroz K. Dubash, a senior fellow at the Center for Policy Research in New Delhi. "This could be the proverbial string which causes Paris to unravel."
The court did not block the rule permanently, but halted it from being carried out in the states until legal challenges against it have been decided, a process that could take a year or more.
Legal experts said the justices' decision to stop work on the rule before any court had decided against it was unprecedented and signaled that the regulation might ultimately be overturned. That could set back the United States' climate efforts for years, although there would still be a chance for Washington to meet its commitments by 2025.
"If the American clean energy plan is overturned, we'll need to reassess whether the United States can meet its commitments," said Zou Ji, the deputy director-general of China's National Center for Climate Change Strategy and International Cooperation, a government think tank in Beijing.
Zou, who was an adviser to the Chinese delegation at the Paris negotiations, said by telephone: "It had seemed that with the American commitments, it was possible to get on the right emissions path globally. But without those commitments, that could be a blow to confidence in low-carbon development. In China domestically, there is also resistance to low-carbon policies, and they would be able to say: 'Look, the United States doesn't keep its word. Why make so many demands on us?'"
Inaction by the United States has long been the chief obstacle to meaningful global climate change agreements.
Obama sought to change that with aggressive but politically controversial Environmental Protection Agency rules to cut planet-warming greenhouse gas emissions from coal-fired power plants. With those rules, Obama won agreements from China and India to enact pollution reduction plans and helped push other countries to sign on to the Paris measure.
The top priority for Prime Minister Narendra Modi of India remains to provide cheap electricity to the 300 million Indians without power. If the U.S. reneges on its commitments, "it really would strengthen the hand of those who say Paris was ineffective and a bad deal for India," Dubash said.
Under Obama's commitment to the Paris Agreement, the U.S. will cut its emissions 26 percent to 28 percent by 2025, largely through the EPA regulations on power plants and a mix of rules reining in pollution from cars, buildings and other sources. All of those policies were set to be carried out briskly so they would be well underway by the time Obama left office.
White House officials insisted on Wednesday that the rule would eventually be upheld, and that given the timetable for litigation and for meeting the target, the U.S. could still achieve its Paris commitment.
A White House spokesman, Eric Schultz, pointed to other greenhouse gas reduction policies Obama had established to help meet the 2025 target, including a federal budget agreement late last year that included long-term extensions of tax credits for wind and solar power.
Still, the Supreme Court's decision ensures that climate policy will not be set on Obama's watch. A U.S. District Court will hear oral arguments on the climate rule June 2 and is expected to issue its decision later this year, but an appeal to the Supreme Court is all but certain. If the justices agree to hear the case, a ruling is unlikely before June 2017.
If the rule is eventually overturned, the EPA is still required by law to put forth a regulation controlling carbon dioxide emissions. That rule would be shaped by the next president and face its own legal gantlet, pushing action years into the future.
The White House and its supporters took hope from announcements that the governors of some states, including California, New York and Washington, would continue to work voluntarily to carry out the rule.
But most states are expected to halt their compliance efforts. Sen. Mitch McConnell, R-Ky. and the Senate majority leader, had already been urging governors to refuse to comply with the plan.
"These regulations are, in my view, likely illegal," McConnell said Wednesday. "Yesterday's Supreme Court order is just the latest sign of that. If nothing else, it shows we were right to let governors know their options."
U.S. policy experts said that the Supreme Court decision might be the first of many fractures in the deal.
"This pushback is not something that's unique to the United States," said John Sterman, a professor of management at the Massachusetts Institute of Technology who attended the negotiations in Paris. "It's happening all over the developed world."
Poland and some other coal-reliant countries have resisted the European Union's commitment under the agreement to more stringently reduce emissions across member states.
Already, some people close to the climate talks worry that the events in the U.S. could lead to a repeat of what happened after the signing of the 1997 Kyoto Protocol, the first major climate change treaty. Vice President Al Gore, a staunch environmentalist, negotiated the treaty with other world leaders, but the Senate voted against it. Then President George W. Bush pulled the United States out entirely.
The Democratic presidential candidates, Hillary Clinton and Bernie Sanders, have pledged to continue and strengthen Obama's climate change agenda, so a rule developed by their administrations would probably let the country meet its Paris goals.
But Republican contenders, including Donald Trump, Sen. Ted Cruz of Texas and Sen. Marco Rubio of Florida, have questioned or denied the science of human-caused climate change and sharply criticized the climate change regulations and the Paris Agreement.
"The Supreme Court just clarified the stakes for the American people in the election when it comes to climate change," said Nigel Purvis, the president of the Climate Advisers consulting group and a climate diplomat under Bill Clinton and George W. Bush.