President Joe Biden is not wasting any time getting going on his new administration’s priorities. He issued another round of executive orders, actions, memorandums and guidance to agencies Thursday — all tied to the nation’s response to the COVID-19 pandemic.

Among the changes: more resources for state and local governments, including resources needed to safely reopen schools, plans to improve collection and sharing of data about the pandemic, and more information about how the administration plans to use the Defense Production Act.

At the same time, the administration is undoing actions and policies of the preceding administration: ending the ban on travelers from several Muslim-majority countries, rejoining the Paris climate agreement and revoking permits for the Keystone XL pipeline.

So what’s in a new president’s toolbox to reverse the work of the previous occupant of the White House?

A new administration can make significant policy changes on day one because of how modern presidents tend to get stuff done. Rather than asking Congress to go along with what they want, presidents use executive agencies they control. And former President Donald Trump really leaned into this strategy.

“A lot of his legacy is through executive action and regulatory choices,” said Aaron Klein, a senior fellow at the Brookings Institution. “That empowers the new Biden administration to undo many of Trump’s policies.”

Making some changes is as simple as signing a document, but changing regulations can be a bit harder. One way to do it is with the Congressional Review Act.

“What it does is it gives the new administration and the Congress 60 in-session days where they can give directive on a rule that needs to be rolled back,” said Nikitra Bailey, a vice president at the Center for Responsible Lending.

Her group felt the sting of the Congressional Review Act in 2017 when a brand-new Trump administration used it to overturn a regulation limiting forced arbitration.

“They actually rescinded it through CRA and literally prohibited kind of class-action lawsuits,” Bailey said. Now the group is pushing to use the CRA to overturn several Trump-era rules.

Another way an administration can change policy is to let outside groups do it for them in court.

“These two regulations that we’re suing about right now, it is important to note that they just went into effect,” said Nick Fish, president of American Atheists. He’s working with other groups to overturn rules about religious influence in social services and at universities.

“Groups like us are out there making sure that any of these changes that the Trump administration tried to jam through in the last few minutes here can be rolled back using these lawsuits,” he said.

Fish said the Biden administration can choose not to fight on behalf of Trump administration rules, making the job potentially easier for his side’s lawyers.