Donald Trump’s administration has undertaken a series of aggressive rollbacks to US environmental protection policy that has broad repercussions not only for the country, but for the rest of the world as well. As the American elections approach, it’s reasonable to ask how easily some of that damage can be undone by a different White House occupant. The answer is not exactly clear.

While US environmental groups clearly hope that candidate Joe Biden will come to power in January, reversing some of the anti-environmental policies enacted under Trump will take more than just a Democratic president and a new batch of federal appointees.

On the one hand, some of the rollbacks can be easily undone. Many have come in the form of executive orders that would presumably be retracted by a new president. Other proposed reversals may still be only in the draft stage by the time inauguration day arrives in January, and thus are just as easily jettisoned by a new administration.

But some of the reversals and new rules that have been concluded under Trump could prove to be more durable. Any new regulations finalized by the administration in the two months before inauguration day would be vulnerable to the Congressional Review Act – a procedure that allows Congress to overturn rules within 60 days of their finalization. To make use of that, however, Democrats would have to maintain their majority in the House and win a majority in the Senate in November’s election.

Trump administration rules that fall outside that timeline would have to be repealed and replaced via a much longer regulatory process regardless of which party prevails – a process involving months of legal analysis, a public comment period, and then likely a lawsuit from the opposing parties or corporations. It is this process, in fact, that has preventing most of Trump’s deregulatory salvos from taking effect.

“If you look at the track record, Trump is losing close to 75 percent of these cases in court,” Kyla Bennett, a former EPA staffer turned whistleblower told The New Republic Magazine. “That’s good news. But the bad news is we are going to be suffering from the same slow-as-molasses justice system to overturn” Trump era rules and reversals of previous protections.

Nevertheless, the assault on environmental regulation has been steady and relentless. In July, the New York Times published its full tally of the 100 rules Trump has sought to undo.  His administration has sought to weaken limits on carbon dioxide emissions from power plants and automobiles and chipped away at many more rules governing clean air, water and toxic chemicals. Several major reversals have been finalized in recent months as the country has struggled to contain the spread of coronavirus.

Below is a list of three of the most internationally significant regulatory rollbacks and reversals Trump has enacted – or is seeking to enact – and an analysis of how easy, or difficult, it would be to reverse them under an administration willing to do so.

1. Withdrawal from the Paris Climate Accord:

The Trump administration’s rollback:

Four months after taking office, President Trump announced his intention to withdraw from the Paris Climate Accord, which has been accepted by all 197 nations within the United Nations Framework Convention on Climate Change. The move had enormous symbolic implications. Because the Paris agreement is non-binding, Trump could have chosen simply not to observe it. Instead, his boastful declaration from the White House of his intention to withdraw telegraphed that he would not only ignore, but hamper efforts to address global climate change.

What it means:

America’s withdrawal left a void in international climate leadership. Other world leaders have tried to continue advancing international progress, but Trump has actively undermined their efforts, and most countries outside Europe are not on track to meet the Paris commitments.

What can be done by Biden?:

The US cannot officially withdraw from the Paris accord until Nov 4, 2020 – one day after America’s election day. Were Biden to win, he could decide to rejoin the Paris accord in his first days in office after the January 20, 2021 inauguration. That reversal process would not take effect for at least 30 days, so the US would have been officially withdrawn from the agreement for less than four months.

2. Vehicle Emissions Standards

The Trump administration’s rollback:

The Trump administration has frozen US Corporate Average Fuel Efficiency (CAFE) standards at what they were nearly a decade ago.

What it means

Transportation accounts for the largest chunk (29%) of American greenhouse gas emissions, at 29 percent. At the same time, the US has among the weakest vehicle fuel efficiency standards in the world. Between 1978 and 1980, after CAFÉ standards were implemented, fuel efficiency standards increased by more than 50%, from 18 to 27.5 miles per gallon.

But as oil prices and interest in environmental protection among political leaders waned, CAFE standards stagnated, with passenger vehicles stuck at 27.5 mpg for the next quarter century, until 2011. That’s when, as part of a bailout from the Obama administration during the Great Recession, automakers agreed to nearly double vehicle fuel efficiency by 2025.

As oil and gas prices have remained relatively low – and because most domestic new vehicle purchases have been for crossover SUVs and pickup trucks – automakers asked the Trump administration to ease the fuel efficiency standards they agreed to under Obama. Trump gave them even more than what they asked for and decided to freeze CAFÉ standards at 2011 levels.

The new proposed rule triggered a legal battle with California. After the administration declined to compromise with the state, the issue morphed into a legal fight that will keep the auto industry in a regulatory limbo for the foreseeable future.

What can be done by Biden?

A Biden administration would probably revive stricter CAFE standards within a year or two of taking office. Such a move – pending the outcome of the November presidential and congressional elections – would amount to a relatively brief hiatus in the nation’s commitment to increasing vehicle fuel efficiency.

3. Obama Clean Power Plan replaced with Trump “ACE” proposal

The Trump administration’s rollback:

Electricity production accounts for the second-largest chunk of U.S. greenhouse gas emissions, at 28 percent. The Obama EPA announced the final version of the Clean Power Plan in August 2015 to regulate electric utilities’ carbon pollution.

In February 2016, the plan was challenged by 27 conservative state attorneys general and it was temporarily blocked by a 5-4 decision of the Supreme Court. The Trump administration took office while legal challenges to the rule were still ongoing.

What it means

Under an earlier landmark Supreme Court decision (Massachusetts v. EPA in 2007), EPA is legally required to regulate carbon dioxide as a pollutant once it concluded that greenhouse gas emissions pose a threat to public health via climate change. As a result, the Trump administration could not simply scrap the Clean Power Plan, but rather was required to replace it. The Trump EPA did that with the dramatically weaker Affordable Clean Energy (ACE) rule, which essentially requires fossil fuel power plants to increase their efficiency rather than mandating that they meet specific carbon dioxide emission levels.

What can be done by Biden?

Because challenges to Obama’s Clean Power Plan remained unresolved by the courts, tackling power sector emissions is expected to be a lengthy and more difficult process for a Biden administration than transportation emissions. Doing so would require drafting, proposing, and finalizing a new plan to replace the Trump ACE rule. Such an effort doubtless would lead to a whole new set of legal challenges, and therefore to more delay and uncertainty.