These empirical groundings for rules are not just made-up. Mr. Pruitt and the incoming Trump administration cannot simply rely on their preferences or on baseless claims about science and markets. Decades of law, much of it created by conservatives’ judicial heroes, requires presidents and agencies to abide by the rule of law and justify regulatory reversals. They have to take a hard look at science and other underlying facts. A ruling by the United States Court of Appeals for the District of Columbia Circuit upholding the Clean Power Plan would further constrain the new president and Mr. Pruitt.

What about a legislative attack? Past blunderbuss efforts to weaken environmental laws through congressional actions by Republicans have met with painful defeat, as former House Speaker Newt Gingrich can attest about his failed mid-1990s rollback efforts. Even narrow legislative bills proposing regulatory turnarounds face filibuster threats under current Senate rules. The Congressional Review Act allows Congress, on an expedited basis, to overturn rules approved in the final days of a presidency, but not rules issued many months or years ago.

On the climate front, many of the reductions in greenhouse gas emissions and cleaner energy innovations have resulted from state initiatives, although some states — like Oklahoma, where Mr. Pruitt is from — resist. Federal law and constitutional norms make federal pre-emption of such state-level leadership illegal under most laws and highly unlikely under any future laws. Even when federal progress falters, states can do more. Climate denialists in charge of the executive branch cannot halt energy and technological transformations already underway, especially when those are a result of state policies and are linked to private innovations.

An E.P.A. led by an anti-regulatory zealot will benefit from deference from the courts, especially when he slows new initiatives, adopts lax enforcement policies, engages in collusive settlements or proposes reconsideration of past actions. Foot-dragging is hard to remedy. However, science, data, statutory requirements, Supreme Court precedents, existing regulations, state progress and the huge clean energy industrial sector will constrain regulatory rollbacks or the wholesale loss of progress to slow climate change. Under the Constitution and rule of law, change by presidential fiat is not an option.