Donald Trump has said he wants to "terminate" spending on what he calls the Green New Deal, presumably referencing the Biden administration's signature Inflation Reduction Act, a major climate law.

Why it matters: Pulling back that money would require congressional action — not a given, as the IRA's popularity has grown — and could result in lost jobs, unfinished factories, and a costly mess for many businesses and states counting on those funds.

Catch up fast: "My plan will terminate the Green New Deal, which I call the Green New Scam. Greatest scam in history, probably," Trump said in a September speech before the Economic Club of New York. "We will rescind all unspent funds under the misnamed Inflation Reduction Act..."

• The campaign said something similar in an email to Axios, blaming his opponent for the policy. "To address the inflation crisis that Kamala has caused and rapidly bring down all prices, President Trump will unleash American energy, terminate Kamala's socialist Green New Deal spending, and cancel her insane Electric Vehicle mandate and Power Plant Rule," wrote senior advisor Brian Hughes.
• Hughes said the "so-called 'Inflation Reduction Act' contributed to the worst inflation crisis in generations." (Inflation began falling from its peak in the months after the IRA passed in August 2022.)
• The campaign didn't offer more on Trump's intentions or clarify exactly what the Green New Deal refers to.

The big picture: The name of the law is misleading, as Trump said. The IRA represents the largest investment in addressing the harms of climate change in American history. A rollback would be a major blow.

• "This was the United States' big shot," says Ernie Tedeschi, director of economics at the Yale Budget Lab, who worked in the Biden White House. Without it, long-term climate challenges are much harder.

How it works: For starters, there are tax credits for individuals and businesses for investing in clean energy projects that could amount to as much as $1.2 trillion, per an estimate from Goldman Sachs last year, over the law's 10-year lifespan.

• Though climate provisions are the centerpiece, the IRA also tackles other issues: It put the $35 insulin price cap in place; allows Medicare to negotiate drug prices, includes billions in funding for the IRS, levies a 1% tax on certain corporate stock buybacks, and establishes a corporate minimum tax.

It's not clear if terminating spending would also mean an effort to eliminate the tax credits or other provisions. The Treasury Department is responsible for writing the rules and regulations implementing the clean energy tax credits. A hostile future administration could try to change those rules.

• That would likely involve a lengthy court battle — but regardless of the outcome it would slow down further spending and create uncertainty for companies trying to plan around tax credits.

And then there's the funding for loans and grants for projects that reduce greenhouse gas emissions and protect against climate change impacts.

• Much of that grant money is out the door or "obligated," meaning contracts have already been signed. White House senior officials tell Axios they've awarded $92.5 billion in grants so far — about 80% of the funding available in the fiscal year that ended in September.
• It would be hard, for a future Trump administration to claw back the funds, legal experts say.

It's the unspent funds that could be in trouble — and the projects that are in a state of limbo, where final contracts haven't been signed.

Trump needs U.S. lawmakers to rescind that money. It's illegal for an administration to refuse to spend funds Congress has appropriated.

Why it matters: That hasn't stopped Trump before.

State of play: Under a 1974 law called the Impoundment Control Act, a president can pause spending or ask Congress to rescind funds — but you can't just not spend money for ideological reasons.

• The law was passed as a response to President Nixon's habit of not spending money on things he opposed.

Where it stands: Trump violated that law before, per the Government Accountability Office, when he withheld military aid to Ukraine during his presidency — an action that ultimately led to his first impeachment.

• Since then Trump has said he wants to overturn the impoundment law to have more power over spending.
• "When I return to the White House, I will do everything I can to challenge the Impoundment Control Act in court, and if necessary, get Congress to overturn it. We will overturn it," he says in a video posted last year on his campaign website. "With impoundment, we can simply choke off the money."

The bottom line: If Trump wants to shut off the IRA spigot, he'll likely find ways to do it.

Talk of pulling back IRA spending recalls the push to repeal the Affordable Care Act. It was an unwieldy slog through the courts and Congress that failed — partly because Americans and businesses warmed to the law.

The big picture: Lawmakers may be loathe to pull the rug out from under constituents and business owners who've reshaped their lives and companies around existing laws.

Already, there's been some softening toward the IRA among Republican lawmakers — none of whom voted for it.

• Nearly four times as much IRA money, $161 billion, is going to Republican House districts as to Democratic ones ($42 billion), a Bloomberg analysis found.
• In August, 18 Republican lawmakers urged House Speaker Mike Johnson in a letter to keep the IRA's energy tax credits in place.
• Many in business and government affairs circles say the jobs these credits bring to red districts will make it hard to totally unwind the law, Axios Pro reported earlier this year.

Businesses like it. Earlier this month, the WSJ reported that oil companies like Exxon Mobil and Occidental like provisions of the law that provide billions of dollars for low-carbon energy projects that the companies are betting on.

• At least seven of Trump's allies and fundraisers hold hundreds of millions of dollars worth of stakes in companies that are benefiting from IRA tax breaks, Reuters reported last week.

The auto industry is banking on the law, too. In an investor day presentation this month, General Motors' CFO said he expected to see about $800 million in benefits from the law this year, "and expand from there."

What's next: A full repeal of the entire law looks less likely, says Neil Bradley, executive vice president and chief policy officer at the U.S. Chamber of Commerce.

• "There's a growing interest in looking at the provisions of the IRA individually and approaching it with a scalpel rather than an ax," he says.
• The chamber wants to see provisions overturned like the Medicare drug price negotiations — criticized as "price controls" — and the new corporate minimum tax and 1% excise tax on stock buybacks.

The bottom line: Taking back a law once it's unleashed isn't so simple.

Joann Muller contributed reporting.

Editor's note: This item has been corrected to reflect that General Motors' CFO said he expected to see about $800 million (not $800 billion) in benefits from the law this year.