Conservatives haven't had many chances to agree with President Barack Obama over the last eight years. So when the former president offers a rare opportunity, the Right should seize hold of it. Oddly enough, President Trump's exit from the Paris climate agreement provided such an occasion.

When Trump was tearing up the agreement in the Rose Garden Thursday (sadly not literally), Obama was teeing up a sort of new decentralized environmental federalism. While he bemoaned the "absence of American leadership" in a public statement, Obama predicted, "cities and states will step up and do even more to lead the way."

Before Trump finished his speech, the Left was following Obama's advice. New York Mayor Bill de Blasio promised to go his own way and Pittsburgh Mayor Bill Peduto followed suit. Democrat Governors Dan Malloy of Connecticut, Terry McAuliffe of Virginia and Kate Brown of Oregon telegraphed that they would soon do the same.

Rather than sneering, conservatives should be cheering this green confab. Wittingly or otherwise, their actions threaten to eradicate the central premise of the Left's regulatory scheme. Under the Obama administration, the federal government was always cast as Captain Planet. For the first time, cities and states are taking the lead.

Both Al Gore and Bill de Blasio endorse this reorientation, describing it not as a temporary provision but as a permanent solution. "Washington will not have the last word on the fate of the Paris Agreement in the United States," Bloomberg wrote in Climate of Hope, a book that Gore strongly endorses. "Mayors will—together with business leaders and citizens from all over the globe."

And for once both the Koch brothers and Tom Steyer should be on the same page. It's an obvious agreement. If San Francisco wants to return to a green agrarian existence, then let them. And if Oklahoma City wants to light their oil wells on fire, let them too.

Any liberal or conservative who experiences damages, as a result, can sue in a court of law, change the regime at the ballot box, or register their dissatisfaction with their feet by moving. It's a bottom-up, federalist approach to solving the challenges of global warming.

Obama and a cast of liberal characters seem confident they can do the job without the federal government. Conservatives should cheer them on for once.

Philip Wegmann is a commentary writer for the Washington Examiner.