WASHINGTON — President-elect Donald J. Trump has selected Scott Pruitt, the Oklahoma attorney general and a close ally of the fossil fuel industry, to run the Environmental Protection Agency, a transition official said, signaling Mr. Trump's determination to dismantle President Obama's efforts to counter climate change.
Mr. Pruitt, a Republican, has been a key architect of the legal battle against Mr. Obama's climate change policies, actions that fit with the president-elect's comments during the campaign. Mr. Trump has criticized the established science of human-caused global warming as a hoax, vowed to "cancel" the Paris accord committing nearly every nation to taking action to fight climate change, and attacked Mr. Obama's signature global warming policy, the Clean Power Plan, as a "war on coal."
Mr. Pruitt, 48, who has emerged as a hero to conservative activists, is also one of a number of Republican attorneys general who have formed an alliance with some of the nation's top energy producers to push back against the Obama regulatory agenda, a 2014 investigation by The New York Times revealed.
At the heart of Mr. Obama's efforts to tackle climate change are a collection of E.P.A. regulations aimed at forcing power plants to significantly reduce their emissions of planet-warming carbon dioxide pollution. It will not be possible for Mr. Trump to unilaterally cancel the rules, which were released under the 1970 Clean Air Act. But it would be possible for a legally experienced E.P.A. chief to substantially weaken, delay or slowly dismantle them.
As Oklahoma's top law enforcement official, Mr. Pruitt has fought environmental regulations — particularly the climate change rules. Although Mr. Obama's rules were not completed until 2015, Mr. Pruitt was one of a handful of attorneys general, along with Greg Abbott of Texas, who began planning as early as 2014 for a coordinated legal effort to fight them. That resulted in a 28-state lawsuit against the administration's rules. A decision on the case is pending in a federal court, but it is widely expected to advance to the Supreme Court.
As Mr. Pruitt has sought to use legal tools to fight environmental regulations on the oil and gas companies that are a major part of his state's economy, he has also worked with those companies. For example, the 2014 investigation by The Times found that energy lobbyists drafted letters for Mr. Pruitt to send, on state stationery, to the E.P.A., the Interior Department, the Office of Management and Budget and even President Obama, outlining the economic hardship of the environmental rules.
Industries that Mr. Pruitt regulates have also joined him as plaintiffs in court challenges, a departure from the usual role of the state attorney general, who traditionally sues companies to force compliance with state law.
The close ties have paid off for Mr. Pruitt politically: Harold G. Hamm, the chief executive of Continental Energy, a North Dakota oil and gas firm that also works in Oklahoma, was a co-chairman of Mr. Pruitt's 2013 re-election campaign.