Fourteen Democratic state attorneys general urged Donald Trump in a letter sent Wednesday to have his administration continue defending President Obama’s Clean Power Plan, a monumental effort to address climate change that is the target of a lawsuit brought by more that two dozen, largely conservative states.

The letter also rebutted the legal arguments that some of the attorneys general suing Obama over the regulations made in their own letter sent to Trump earlier this month. The signees threatened to sue Trump if he followed those red state officials’ advice to simply instruct the Environmental Protection Agency not to enforce the climate plan.

“In summary, we advocate that you reject misguided advice that the Clean Power Plan be discarded; advice that, if followed, would assuredly lead to more litigation,” the letter read. “Instead, we urge you to support the defense of this critically-important rule and the implementation of its carefully constructed strategies to reduce emissions from the nation’s largest sources.”

Lawyers representing a handful of cities and counties, like South Miami, Florida and Boulder, Colorado, also signed onto the letter.

How to handle the lawsuit against the Clean Power Plan is just one of a number of decisions Trump’s Justice Department will have to make about legal cases against Obama’s actions.

A federal appeals court heard arguments in the lawsuit against the Clean Power Plan earlier this year and could issue an opinion on the matter before Trump’s inauguration. The Supreme Court had paused implementation of the regulations last February, before the death of Justice Antonin Scalia, and said in its order that the regulations would remain halted until those involved in the lawsuit had a chance to appeal the impending appeals court decision to the Supreme Court.

“If the challengers are so confident in their oft-repeated claim that the Clean Power Plan is ‘unlawful,’ why not let the court decide the claims that they themselves brought?” the letter from Democratic attorneys general read.

The letter also pushed back on the idea put forward by the red-state attorneys general that Trump could “resolve” lawsuits against the climate plan rather than continue to fight them.

“Be assured that we would vigorously oppose in court any attempt to remand the Clean Power Plan back to EPA so late in the litigation, and prior to a decision from the Court on the merits of the claims,” the letter read.

As the Washington Post reported, Trump could also take a more long-term approach to dismantling climate change action by using the slow-moving administrative process to rewrite the Obama-era regulations

Trump has said that climate change is hoax created by the Chinese, but earlier this month, he and his daughter, Ivanka, met with former vice president Al Gore, a vocal advocate in the fight to combat global warming, to discuss the issue.