President Joe Biden has put his team to work reviewing dozens of actions taken by former President Donald Trump, aiming to reverse orders that he says harm the environment or endanger public health. For the energy and auto industries, the impact could be far-reaching. But legal experts warn that it could take two to three years — and in some cases, most of Biden’s term — to put many of the old rules back in place.

“People should temper their expectations about what can be done quickly,” said Kevin Minoli, who served as a lawyer at the Environmental Protection Agency in the Clinton, Bush, Obama and Trump administrations. He added, “It’s very possible, more possible than not, that some of the Trump rules will still be in effect for a couple of years.”

Biden aims to reduce harmful emissions from cars, trucks and SUVs. Oil and gas operations are being scrutinized as well from how companies extract resources from the ground to the safety of pipelines that distribute the fuels. The new president aims to transition the country to 100% renewable energy for electricity generation by 2035 and net-zero emissions in the overall economy by 2050. His campaign website promises to develop rigorous new fuel economy standards and eventually make all light- and medium-duty vehicles electric, though it provides no time frame. During his campaign, Biden also spoke about restricting oil and gas drilling on federal lands and reducing methane emissions from oil and gas operations.

Mr Biden has an array of legal tools to reinstate environmental protections that were dismantled by the Trump administration. Gina McCarthy, his top domestic climate change adviser, headed the E.P.A. in the Obama administration and served as the chief author of some of the nation’s most comprehensive climate change rules. She has now reviewed every possible option to restore those protections, according to a White House official who is familiar with her thinking but was not authorized to speak on the record.

Many experts agree that Biden’s actions could help the nation achieve ambitious climate goals and further enhance the renewable energy sector, driving job growth. Others say they worry more that stricter regulations could hurt companies struggling to recover from the pandemic, which decimated demand for fuel.

Under President Barack Obama, oil and gas operations were required to inspect equipment built or modified after 2015 twice a year for methane leaks and fix leaks that they found. Trump weakened those rules. Now, Biden is expected to restore Obama-era methane regulations. He may also extend those requirements to those older wells, which could put some operators out of business.