The recent court decision Halbig v. Burwell — in which a three-judge panel struck down an important provision of the Affordable Care Act was a glorious victory for conservative typo hounds. They went over the ACA with a fine-toothed comb looking for ways to damage the policy and got part of the D.C. Circuit Court of Appeals to agree with their reasoning.

Could conservatives repeat that tactic with other laws? Josiah Neeley recently made the case here at The Week, arguing that because of a drafting error in amendments to the Clean Air Act, the EPA's proposed rules on coal-fired power plants could be overturned:

Ordinarily, when the House and Senate pass different versions of the same bill, any discrepancies are reconciled by a Conference Committee. In this case, however, the Committee was asleep at the switch, and included both the House and Senate amendments to the language in the final bill. Since the two versions of the language are inconsistent, this has created a bit of a statutory puzzle. The U.S. Code includes the House language. The EPA, by contrast, has long maintained that the Senate language is what governs.

This matters, because under the House language, the EPA's Clean Power Plan would be illegal, since the EPA has already issued regulations under 112 of the same "source category" as the existing power plants covered in the new rule. [The Week]

But after speaking with several legal experts, I think the EPA is probably safe. There are two main defenses.

First is the Chevron standard. Ambiguous language is fairly common in U.S. law, so the Supreme Court, in the case Chevron vs. NRDC, established a method of resolving such discrepancies. Under Chevron, if there is some ambiguity in the language of the statute, courts must determine whether an agency's actions are based on a reasonable interpretation. If they are, then the courts must defer to the agency in question.

The U.S. Code contains only the House version of the bill. But the "Statutes at Large," which is the ultimate authority, contains both. Thus, there is a strong argument that the EPA deserves Chevron deference in this instance. This isn't a case of language that can be read in two different ways — it's literally two different versions of the paragraph. A more obvious case of statutory ambiguity would be hard to imagine.

Second, it's not at all clear that the House language would, in fact, close off regulation of carbon pollution from coal-fired power plants. Here is the language in question, from section 111(d):

…each State shall submit to the Administrator a plan which (A) establishes standards of performance for any existing source for any air pollutant

(i) for which air quality criteria have not been issued or which is not included on a list published under section 7408(a) or emitted from a source category which is regulated under section 7412 of this title, but

(ii) to which a standard of performance under this section would apply if such existing source were a new source.

Neeley says this clause was explicitly designed to forbid dual regulation of emission sources. The idea is that because the statute says states have to submit a plan for sources of air pollutants that haven't been regulated, then any sources of pollutants that have been regulated for anything else at all are off limits.

Indeed, a recent lawsuit from 12 state attorneys general argues that because coal-fired power plants are already regulated for mercury emissions under section 112 (the 7412 reference above), their carbon dioxide emissions can't be regulated.

But that is a huge logical leap. After all, the section doesn't say, "The EPA shall not regulate pollution sources already regulated elsewhere." One can also read it as filling a regulatory gap — making sure that air pollutants that don't fit under section 109, 110, or 112 (which define more traditional sources of pollution, like smog or cancer-causing agents) may also be regulated. In this view, section 111(d) forbids only dual regulation of particular pollutants, not sources in general.

This interpretation fits much better with the broader context of the Clean Air Act (and is how the Senate version reads). Forbidding dual regulation of sources would practically gut the bill's authority to regulate carbon dioxide at all, since just about all of the major sources have already been subject to some other regulation. "There is no actual indication that the House was trying to do a different thing than the Senate," says James Wrathall, counsel at Sullivan & Worcester.

Such a view is also supported by Supreme Court rulings. In Massachusetts vs. EPA, the court held that carbon dioxide and other greenhouse gases are indeed air pollutants, and that the EPA is obliged to regulate them. In American Electric Power Company vs. Connecticut, the court ruled that private power companies can't be sued for carbon dioxide emissions as a public nuisance, because the EPA is responsible for regulating those emissions. Both of those rulings make no sense if section 111(d) effectively forbids any regulation of carbon emissions from sources otherwise regulated.

Most striking of all, the argument by the attorneys general would make a total hash of the most recent Supreme Court ruling on EPA greenhouse gas regulations, Utility Air Regulation Group vs. EPA, which was handed down only a few weeks back. The ruling held that the agency could regulate large, stationary sources of greenhouse gases only if they are already regulated for emitting conventional pollutants.

In any case, the first round of lawsuits against the EPA will almost certainly be thrown out because the EPA hasn't even issued its final rule.

If this latest effort to secure conservative policy goals through the courts is going to be anything more than a nuisance to the EPA, conservatives are going to have to come up with something much stronger.