Environmental Protection Agency chief Scott Pruitt the former Oklahoma attorney general who made his name by suing the agency more than a dozen times and says he does not agree that human activity is a primary contributor to global warming isnt even enough of a hard-line climate change denier for some players in President Donald Trump s administration.

A schism is brewing within the administration over what to do about a somewhat-obscure EPA ruling that, for the last eight years, has been the bedrock of policy to fight global warming: the scientific conclusion that greenhouse gases cause climate change, which is bad for humans and should be regulated.

A 2007 Supreme Court ruling found that the agency is obligated to regulate any type of air pollution that may reasonably be anticipated to endanger public health or welfare under the 1970 Clean Air Act. The George W. Bush administrations EPA determined that greenhouse gases were, in fact, a danger, but decided not to do anything about it . The Obama administrations EPA took the issue up shortly after taking office and, in December 2009, issued its conclusion commonly called the endangerment finding which compelled the agency to start regulating those emissions.

The endangerment finding is the foundation of all of Obamas global warming regulations, including the Clean Power Plan, which strictly limits emissions from power plants, the major contributors of U.S. emissions .

With an executive order signed Tuesday, Trump began the process to dismantle the power plant rules, which the Supreme Court had already blocked in response to the state lawsuits Pruitt spearheaded in his previous job.

However, the order Trump signed made no mention of the endangerment finding. Its unclear if earlier drafts had addressed it, since the Trump campaign had said in written statements that he would overturn the finding, but it was Pruitt who argued against including it, Politico and CNN reported, insisting the language would trigger a difficult, years-long legal battle.

Pruitts approach puts him at loggerheads with Myron Ebell, the emphatic climate science denier who led Trumps EPA transition team. Soon after the inauguration, Ebell, who oversees global warming and environmental policy at the libertarian Competitive Enterprise Institute, submitted a petition to the EPA requesting the agency reconsider the endangerment finding. The EPA has yet to respond. On Thursday, Ebell accused the White House of playing hot potato with a process he says is critical to prevent courts or a future administration from policing greenhouse gases, which he does not believe cause global warming.