President Barack Obama hadn’t even made it home from climate talks in Paris when Republicans in Congress voted to kill the regulations backing his carbon-cutting pledge.

Obama’s foes want to undercut any climate accord from the United Nations summit in Paris, along with his credibility on the issue. But just as with the Republicans’ failed attempts to kill Obamacare, the efforts are likely to run aground over constitutional and legal constraints.

Even a Republican successor in the White House would have a hard time overturning whatever commitments are made in coming days or the U.S. power plant rules that underlie Obama’s pledge and were targeted by Tuesday’s resolutions, now facing an almost-certain veto.

“The Republicans might get some political talking points by saying this, but realistically, there’s no way they are going to repeal these rules if the courts uphold them,” said Brian Potts, a Foley & Lardner LLP attorney specializing in Clean Air Act cases.

The White House has pushed an approach in Paris that ensures any final deal won’t hinge on a ratification vote in the Senate. Unlike other international accords, it would not be subject to the chamber’s “advice and consent.” Individual countries’ carbon-cutting commitments are not expected to be legally binding, and in the U.S., Obama is relying mostly on executive branch regulations to fulfill a promise to pare emissions at least 26 percent below 2005 levels over the next decade.

Power Plan

That includes the Environmental Protection Agency’s Clean Power Plan to throttle carbon dioxide emissions from the power sector, effectively blocking construction of new coal-fired power plants.

But Obama still needs Congress to go along with his promise to deliver $3 billion into a United Nations fund to help developing countries adapt to rising seas and other impacts of climate change. And scores of lawmakers have told the president they won’t pay the bill.

“Congress ultimately holds the power of the purse,” according to a letter to Obama last month from 37 U.S. senators, including Republicans John Barrasso of Wyoming and Jim Inhofe of Oklahoma. “Congress will not allow U.S. taxpayer dollars to go to the Green Climate Fund until the forthcoming international climate agreement is submitted to the Senate for its constitutional advice and consent.”