On Thursday, representing coal company Peabody Energy, Laurence Tribe will argue in federal court that the EPA’s Clean Power Plan, which would cut the country's greenhouse gas emissions on a state-by-state basis, might be unconstitutional. That a big company would retain the services of an elite lawyer to advance its interests is dog-bites-man material, but Tribe’s involvement has turned boring legal advocacy into a political melodrama because: In addition to being a storied legal thinker, Tribe was also once mentor to a Harvard Law School student named Barack Obama.

When Obama became president, Tribe worked in his Justice Department. Now, Tribe is allowing himself to be used as a weapon in the partisan battle against climate change mitigation. Liberals are seething, but they’re also in an apparent bind. Tribe’s argument—that the EPA is using its regulatory power to coerce states into reducing carbon emissions from power plants—bears superficial similarity to a legal argument that might save Obamacare.

In King v. Burwell, which the Supreme Court will decide in June, the challengers claim that the Affordable Care Act statute doesn’t authorize insurance subsidies in states that don’t set up their own exchanges. It’s a weak argument in its own right, but even if it were correct, it would create a big constitutional problem. In the right’s imagination, Obamacare isn’t a law that encourages states to set up insurance exchanges, and steps in to create them in states that decline; it’s a law that threatens to render insurance markets unworkable in states that don’t help implement a universal coverage scheme. In our federalist system, the government can create incentives for states to adopt policies, but it can not command or coerce states into doing so—say, by threatening to send uncooperative state insurance markets into death spiral. 

Testifying before Congress last month, Tribe himself traced a parallel between this and the Clean Power Plan.

“The federalism principles at issue here are strikingly similar to those that arose in the Affordable Care Act case of King v. Burwell, argued in the Supreme Court on March 4,” he said. “There, Justice Kennedy, among others, noted the ‘serious constitutional problem’ that would result if a federal statute were interpreted as threatening the citizens of a State with significant injury unless the State agreed to follow federal policies. This case involves the same pressures on States to knuckle under to the Federal Government, and the same lack of clear notice. EPA’s plan confronts the States with an unforeseeable choice and essentially remakes the agreement between them and the Federal Government that has existed since the Clean Air Act was enacted in 1970.”

Intentionally or otherwise, Tribe was posing a challenge to his liberal critics: If you believe Obamacare’s challengers have read the ACA in an unconstitutional way, then take your complaints elsewhere, because Obama’s climate regulations are no different. And if he were right, he’d be confronting liberals with the greatest Sophie’s choice in recent political memory, wherein one of Obama's biggest legacies might survive at the expense of the other.

In one procedural sense, Tribe is correct. If Obamacare withstands the King challenge on federalism grounds, conservatives will turn around and use the Court’s decision as a weapon against the Clean Power Plan. (Though as Tribe’s involvement suggests, they’re going to use constitutional arguments against the plan no matter what happens in King.) And federal judges determined to use a federalism ruling in King to support an opinion voiding EPA's plan can do just that if they want. “If the King plaintiffs’ interpretation of the ACA is coercive,” posits King architect Jonathan Adler, “then so too is the EPA’s interpretation of the [Clean Air Act].”

But as a purely intellectual matter, there’s very little resemblance between the two. Liberals can support a Supreme Court decision upholding ACA subsidies on federalism grounds and full implementation of the Clean Power Plan, and there need be no contradiction.

King challengers’ interpretation of Obamacare is exceedingly strange, which in turn makes it difficult to weaponize against other regulatory programs in an honest way. King posits that Congress sought to create universal health care programs on a state-by-state basis by threatening to ruin insurance markets—to frustrate their ultimate universal health care goal—in non-capitulating states.

The Clean Power Plan is nothing like that. It encourages states to implement plans to reduce greenhouse gas emissions, and says the federal government will step in and implement a different plan toward the same end in states that decline. Tribe describes the federal fallback derisively when he says, “EPA claims the power to impose severe sanctions, including the loss of highway and Clean Air Act funds, as well as the imposition of a centrally planned and administered federal scheme that could harm not simply the State but also its citizens and economy.”

But even on his own terms, this is nothing like the coercive scheme at issue in King. For the parallel to hold, the EPA would have to be encouraging states to implement their own clean power plans by threatening to exacerbate pollution in states that don’t, or something similarly counterproductive.

“If the Clean Power Plan example looked like King vs. Burwell,” University of Michigan law professor Nicholas Bagley told me, “what you’d have is a federal scheme that didn’t provide power to people, didn’t reduce emissions, and torched the energy market in each state.”

Boston University law professor Abby Moncrieff is of a similar view. In a detailed post on Harvard Law School’s website, she explains why King and the Clean Air Act, from which EPA derives its authority to implement the Clean Power Plan, are nothing alike. 

Under the plaintiffs’ read, this is Obamacare’s threat: “If you set up an exchange (task 1), we will enforce a rational set of insurance market regulations in your state, some of which will apply both on and off the exchanges (our choice of how to do task 2), but if you rely on us to set up an exchange (back to task 1), we will enforce a destructive set of insurance market regulations in your state (a punitive version of task 2).” That structure would be brand new to cooperative federalism, and it would be a transparent attempt at coercion.

The irony that Obamacare might survive on states' rights grounds has created an opportunity for conservatives to pit liberals against one another. But there really is something unique about the King challengers’ interpretation of the ACA. You can believe it’s unconstitutionally coercive—that Congress shouldn't threaten states with insurance market death spirals and crippled energy markets—without weakening the foundation of other important federal regulatory schemes. Because no other federal regulatory schemes actually work that way.

Correction: A previous version of this article stated that Tribe argued in federal court on Wednesday. The EPA case is scheduled for Thursday.