By Tessa Berenson
November 17, 2016

It really is a new day for U.S. energy policy. The President-elect has pledged to roll back environmental regulations, invest in new pipelines and allow drilling on public lands–and he can make many of the changes unilaterally once in office. On their own, Trump’s appointees can issue drilling permits and approve pipelines, including the Keystone XL oil pipeline, which President Obama rejected last year. Trump can begin to scuttle some emissions regulations, like standards for smog, mercury and coal ash, through a new rulemaking process.

Trump will also be able to change the direction of legal fights over clean air. In February, the U.S. Supreme Court blocked the Clean Power Plan, a set of federal regulations designed to curb carbon emissions from coal-fired power plants. It’s now the subject of a battle in a lower court. Trump could try to kill the plan by declining to defend it, appointing an industry-friendly Justice to the Supreme Court or asking Congress to write new legislation.

He may have more trouble fulfilling his pledge to withdraw the U.S. from the Paris climate agreement. Participating nations must wait four years to quit the pact. But in the meantime, Trump could withhold funds earmarked for the implementation process or ignore the targets for U.S. emission cuts laid out in the deal.

All of which is cause for cheer among drillers and miners, but not environmental activists. Trump, warns the Sierra Club’s Michael Brune, “could be devastating for our climate.”

This appears in the November 28, 2016 issue of TIME.

Write to Tessa Berenson at tessa.berenson@time.com.

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