Scott Pruitt, Donald Trump’s choice to lead the Environmental Protection Agency, may find it difficult to deregulate many of President Barack Obama’s climate protection initiatives. 

Though a Republican Congress could overturn some of Obama’s last-minute “midnight” regulations with a simple majority vote, longer standing rules like the Clean Power Plan could prove tougher to cut, according to Reuters. 

Democrat-controlled states like New York and California have promised drawn-out legal battles should Pruitt try to gut laws regulating greenhouse gas emissions.

New York Attorney General Eric Schneiderman, a Democrat, said in a statement that he is “leading a coalition of states that is already aggressively fighting back against efforts to reverse the progress this country has made in combating climate change over the past eight years.”

Schneiderman, who called Pruitt an “agent of the oil and gas industry,” also reportedly has the support of California Democratic Gov. Jerry Brown.

But Pruitt isn’t new to the scene.

The Oklahoma attorney general has concentrated his efforts on suing the very agency he is set to lead, much to the dismay of environmental groups. In 2015, after filing a suit challenging new EPA regulations, Pruitt released a statement explaining his resistance.

“The so-called Clean Power Plan threatens the reliability and affordability of power generation across the nation,” Pruitt wrote, “because it unlawfully coerces states into shuttering fossil-fuel-generated electricity to meet the standards proposed in the rule.”

If Pruitt is looking for a workaround, he could lobby to reduce the agency’s funding overall, making it impossible to enforce existing regulations. But despite Trump’s campaign promises to cut back, curbing federal spending has never proved easy.