There will be plenty of time for deep thinking on the policy ramifications of last night’s surprising election result. Until then, here’s a quick summary of the likely impact of the Trump administration on climate and environmental policy.
1) The Clean Power Plan
The Clean Power Plan, enacted by EPA under the Clean Air Act, is the most significant federal carbon-reduction measure to date. Trump has promised to scrap it. The CPP, however, is a final rulemaking and is therefore federal law. It cannot be discarded at the stroke of a pen. However, Trump does have two possible paths to doing so.
First, Trump could simply refuse to defend the CPP, which is currently being challenged in federal appellate court. DC Circuit oral arguments took place in September, and an opinion is expected sometime next year. If the DC Circuit rejects the CPP, Trump could refuse to appeal to the Supreme Court, and the rule would die.
Alternatively, Trump could undo the CPP through another round of notice-and-comment rulemaking. Agencies are permitted to change their mind, regularly do so, and at least in theory receive the same deference from courts that they do when making rules from scratch. The Trump EPA would have to acknowledge the change in position and provide reasons, but courts would defer to the agency’s technical judgment and (to some extent) reading of the law. This new rulemaking process would take months, possibly years. Since the CPP does not come into effect for a few years, however, this delay wouldn’t matter much. The rule would remain in legal effect but would be a dead man walking.
Both approaches have further legal consequences. If the CPP does survive in the DC Circuit, Trump could in theory mount a weak defense at the Supreme Court. This is probably unnecessary, however - industry opponents would likely hold off on an appeal to the Supreme Court under the assumption that Trump would withdraw the rule. If he does so, environmental groups will surely sue, arguing that the decision to reverse course was arbitrary and therefore illegal. Such a suit would be an uphill battle, but back-and-forth rounds of litigation and rulemaking dragging on for years are possible. Look at the long fight over snowmobile use in Yellowstone for an example, and imagine what higher-stakes litigation will be like.
2) The Clean Air Act
An alternative (or additional) approach is to strip climate change authority out of the Clean Air Act entirely. This is not a new idea - Republicans in Congress repeatedly introduced legislation to do so during the Obama Administration. Those bills were never going to be signed by Obama and never came close to a veto-proof majority. But I assume Trump would indeed sign such a bill. If so, the only real federal climate policy tools will be lost until and unless a future Congress passes new legislation.
There are two reasons to suspect this won’t happen. One is that it’s no longer a priority without Obama in the White House - there’s no need to restrain Trump from using the Clean Air Act on climate in ways that Congress doesn’t like. The other is that Senate Democrats would likely filibuster the bill. However, I can make counterarguments to both of these suggestions. Republicans may still see Clean Air Act revisions as important because they limit the powers of future presidents as well. It’s also possible there is a path to 60 votes, starting with Joe Manchin (D-WV), a noted opponent of carbon regulation. Another 8 Democratic votes might seem hard to find, but perhaps CAA revisions as part of a broader infrastructure bill could persuade them.
3) Other rules
The Obama administration has finalized a number of other environmental rulemakings, such as limits on methane emissions from oil and gas wells, and the “Waters of the United States” rule defining federal jurisdiction under the Clean Water Act. Should Trump decide to retract these rules (as he has promised for the WoTUS rule), the process would be the same as that described above for the Clean Power Plan - a new rulemaking would be needed, and would be subject to litigation.
Past experience suggests that a more likely approach to lower-profile rulemakings is to slow-walk or halt enforcement, rather than explicitly reversing them. This, too, can be litigated, but judicial deference to agencies’ prioritization of commitments and allocation of resources makes such cases even harder to win than those against reversed rulemakings, despite the fact that the legal claim (failure to enforce the law) is superficially stronger.
Trump has promised to “cancel” the Paris Agreement on climate change. In one sense, this is impossible - Paris is an international agreement, and Trump can no more “cancel” it than, say, the Geneva Conventions. He can, however, withdraw from the agreement. Paris is an executive agreement, not a treaty ratified by the Senate. There is legal ambiguity over whether a President may unilaterally withdraw from a treaty, but no question that he may withdraw from an executive agreement. In this sense, Trump could therefore “cancel” US participation in the treaty, including its obligation to submit and meet a “Nationally Defined Contribution” or NDC. The Paris Agreement technically prohibits withdrawal for four years, but there is no real mechanism preventing US refusal to comply.
However, the agreement would remain in force for other countries. Therefore, there's an argument that US withdrawal wouldn't have much effect. As Andy Revkin points out, China is the largest carbon emitter and most projected emissions growth is in developing countries, notably India. US emissions are declining for reasons that have little to do with federal regulation. Some have even suggested that the Clean Power Plan would not be binding - though it would undoubtedly have provided an important backstop against a reversion to coal in the event of increased natural gas prices.
The GOP has long suggested that US action on climate is irrelevant. We may now get to see whether they are correct. In my view, that is a shockingly reckless risk to take, but it is within the power of our new President to do so. Chris Mooney at the Washington Post has more on Trump and Paris here.
5) Institutional Change
As Brad Plumer notes, this is a President who has publicly declared climate change to be a Chinese hoax and suggested doing away with the EPA entirely. Speaking as a lawyer, I don’t have much to say about either. Scrapping EPA would of course require new legislation, though filling top positions with appointees that do not believe their jobs should exist would do a lot to neuter the effectiveness of the agency. Tyler Cowen is cautiously optimistic that Trump will govern in a greener way than his campaign suggests. Whether that is a realistic hope remains to be seen.