I asked legal experts across the political spectrum what Pruitt could do to roll back the Clean Power Plan, and the answers converged on two main options:
1) Don't regulate CO2 from existing power plants at all. The most drastic step Pruitt could take would be to repeal the Clean Power Plan and replace it with … nothing. The government wouldn't regulate carbon emissions from existing power plants at all. (The EPA would still regulate CO2 from other sources however.) This is a bit of a legal gamble, however, and it deserves more explanation.
When Obama's EPA wrote the Clean Power Plan, it claimed authority to do so under Section 111(d) of the Clean Air Act, which allows the agency to set standards for existing sources of pollution (as opposed to new sources). But there was a weird, troubling loophole here.
See, back in 1990, the House and Senate each approved slightly different wordings of Section 111(d) — and, due to a clerical oversight, never reconciled them. According to critics, the House's version basically implies that the EPA can't regulate CO2 from existing power plants under 111(d) because it's already regulating mercury pollution from those same plants under a different section of the law, section 112. The Senate's version basically says it's fine. And it's not clear which version should prevail.
This is one of the key legal disputes over the Clean Power Plan being heard before the DC Circuit Court right now — and we're still awaiting a decision. The court could either rule that a) the EPA definitely has the authority to regulate CO2 from existing plants under Section 111(d), b) it definitely does not, or c) the law is ambiguous and it's up to the agency to decide which interpretation is correct.
So Pruitt could try to argue that the EPA has no authority to regulate CO2 from existing power plants — and just repeal the Clean Power Plan entirely. (The EPA's endangerment finding would stay intact and the agency would still be required to regulate CO2 from new power plants and cars, since those are separate legal issues.) But this only works if the courts agree with his interpretation of the underlying law. If they don't, Pruitt won't get very far with this approach and will have to try something more subtle.
2) Rewrite the Clean Power Plan to be much weaker. As an alternative, Pruitt could say, okay, the EPA has the authority to regulate CO2 from existing power plants. But the specific way Obama went about it was inappropriate — and EPA should scale it back.
Here's how this would work. In order to regulate existing power plants, the EPA had to identify a "best system of emissions reduction," setting state targets based on what's technically feasible and cost-effective. Obama's EPA got creative with this and set emissions targets by assuming that states could a) improve the efficiency of their existing coal plants, b) shift from coal to cleaner natural gas, and c) add more renewable energy to their grids.
This allowed Obama's EPA to require sweeping emission cuts. But it was also controversial, because the EPA was assuming that utilities could reduce emissions at individual power plants by taking actions outside of those power plants (e.g., reduce emissions at coal plants by replacing them with wind farms and gas turbines elsewhere). Opponents challenged this feature in court, arguing that the EPA should only look at measures that can be undertaken at the plants themselves (i.e., actions "within the fenceline"), which would lead to a much weaker rule.
So Pruitt could try to replace Obama's Clean Power Plan with a more modest version that stays within the fenceline. This new rule might assume that utilities can upgrade the heat rate or efficiency of individual coal plants but wouldn't have to do anything else. This would allow the EPA to set much weaker CO2 targets for states — allowing them to make a few modest tweaks to their coal plants rather than embark on the wholesale shift away from coal envisioned by the Obama administration.
Would this be legally defensible? That's unclear. Environmental groups and other opponents might argue that focusing solely on coal plant tweaks isn't actually the best system of emission reduction — and Obama's Clean Power Plan is a superior approach. It'd be up to the courts to decide. But if Pruitt wanted to scale back Obama's climate policy and slow the decline of the coal industry, this would be his best bet.