I didn’t set out to spend all week endorsing Jonathan Chait posts, but he’s got a follow-up to the cover story he wrote last week and, well, I endorse it. Like Chait, I continue to believe that Obama’s EPA will issue CO2 standards on existing power plants. At the very least, there’s no dispositive evidence that it won’t. And I too believe that those standards are the most important piece of Obama’s climate legacy, if not his overall legacy.

But Chait passes over a key fact that, to my eternal puzzlement, plays little role in the discussion about EPA rules. Quite simply, EPA is legally obligated to issue these rules.

I said it all in a post I wrote early last year, but to recap:

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1. In 2007, the Supreme Court ruled in Mass v. EPA that CO2 qualifies as a pollutant under the Clean Air Act.

2. In 2009, EPA issued an endangerment finding that deemed CO2 a threat to public health.

Once those two things happened, a cascading series of of legal obligations was set into motion.

3. First, EPA must regulate “mobile sources” of CO2 under Section 202 of the Clean Air Act. That’s what it did with its new auto mileage standards.

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4. Then, EPA must regulate “stationary sources” of CO2 under Section 111 of the Clean Air Act. First it will issue standards on new power plants. It issued a draft regulation last year, but it missed a deadline in April for issuing the final rule (for which some green groups are suing it). Supposedly it has delayed release of the final regulation so it can do more work to protect the rule against legal challenge.

5. Then, EPA must regulate existing stationary sources — in the case of CO2, primarily power plants — under Section 111(d). That rule, the 111(d) rule, is the one EPA keeps telling journalists it has “no current plans” to develop, and no surprise, since it’s got its hands full working on the rule for new power plants.

Again, this series of executive actions is prescribed by statute. EPA is not “bypassing” Congress, or going around it, or in any way exceeding its authority. It is not even acting on Obama’s discretion, not really. It is simply carrying out the will of Congress, as embodied in the Clean Air Act.

Yes, EPA can slow-walk this, maybe even enough to punt rules for existing CO2 sources to the next administration (though I don’t think it will). Or it could conceivably issue toothless rules (this I’m 50/50 on). Or it could issue good rules and see them struck down by a reactionary D.C. Circuit Court, a disturbingly plausible outcome.

But what it can’t do is just decide not to issue existing-source rules. The agency is under statutory obligation to do so and would be subject to lawsuit if it didn’t. Neither Obama nor EPA has the authority to decline to issues these rules.

The Savvy Washington Insiders of the political press don’t understand or care about policy, they only care about court intrigue, so they are suckers for the daft conservative narrative that EPA regulation of carbon is some quasi-dictatorial power grab that Obama is contemplating. Now, as usual, they’re busy being amateur Sun Tzus and gaming out whether and how he will screw enviros over.

Who knows, maybe enviros — and the planet — will get screwed in the end. It’s usually a safe bet in D.C. But whatever happens, rules on carbon from power plants are coming. On that, Obama has no choice.

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