One of Donald Trump's first priorities as president will be to dismantle President Obama's signature climate rule, says a former Environmental Protection Agency official.

"It's virtually certain that the Clean Power Plan will be revoked. The question is how," said Jeff Holmstead, a partner at the law firm Bracewell and a former assistant administrator at the EPA, speaking on a post-election conference call.

In May, Trump outlined an action plan for his first 100 days in office. Terminating the climate rule made the top of the list. 

"We’re going to rescind all the job-destroying Obama executive actions including the Climate Action Plan," it read.

Experts say it will be a primary focus for the Trump transition team.

President Obama released his climate action plan in 2013. It outlined a broad set of executive actions to regulate power plant and automobile emissions, accelerate permitting for renewable energy, set emissions targets for government facilities, cap methane emissions, and establish efficiency standards for equipment and buildings.

The Clean Power Plan -- a flexible set of rules established by the EPA to regulate carbon dioxide pollution in the states -- was the central pillar of the strategy. 

Holmstead said that Trump's team is already working on a legal plan to kill the rule.

"I’m quite confident that they do intend to make good on that promise. The question is how they will do it -- and will they do it in a way that will withstand legal scrutiny," he said.

Implementation of the Clean Power Plan is currently at a standstill while a D.C. Circuit court determines the legality of the rule. If the court determines that EPA overstepped its legal authority, the Trump administration would simply let the regulation die. If the rule is upheld, the administration would need to establish another rule revoking the Clean Power Plan.

"They would need to explain their rationale. That will be subject to legal challenge," said Holmstead.

In other words, the legal back-and-forth could continue well past Trump's first 100 days.

Merrill Kramer, chair of the sustainable energy practice at the law firm Sullivan & Worcester, agreed that legal challenges could be coming from all angles.

"A Trump-appointed EPA will make every attempt to restrict or repeal the Clean Power Plan. Trump Supreme Court nominees will likely vote to overturn CPP, and a Trump Justice Department will decline to defend CPP in the courts," said Kramer in an email. 

And there's another option: delay.

The Trump administration could simply find ways to stymie implementation. "He can just slow-walk it -- not have staff work on it," said Katherine Hamilton, a partner with 38 North Solutions.

That's the likely strategy for the Paris climate agreement, which Trump also said he would abandon. "We’re going to cancel the Paris Climate Agreement and stop all payments of U.S. tax dollars to U.N. global warming programs," read his plan released in May.

Because the Paris Agreement is not legally binding, the Trump administration could simply ignore the goals negotiated by the Obama administration. That would be much easier than opening up new negotiations, said Holmstead.

"It's unlikely that he will take on the international community to try to renegotiate the Paris climate agreement," he said. "There would be no practical reason to do so."

Finally, Trump will likely start going after any pending efficiency regulations at the Department of Energy. He spelled that out in his 100-day plan as well. 

"That is something that will be a key area of focus of a transition team -- to see how to put a halt to [DOE efficiency standards]," said Salo Zelermyer, a senior counsel at Bracewell.

But first, the big fish: "The Clean Power Plan has to be issue number one," said Zelermyer. 

Hillary Clinton planned to finish what President Obama started on executive climate action. Trump's plan is to end it as quickly as possible.

That doesn't mean that a Trump administration would outright attack renewables, said Kramer.

"Renewables are a significant economic and jobs driver in the U.S.," he said. "It is thus more probable that a Trump administration will be pro-all energy resource development rather than undertaking anti-renewables initiatives. In short, the renewables train has left the station."