O n October 23, 2015, the U.S. Environmental Protection Agency (EPA) published its final Clean Power Plan rule (CPP or Rule) to regulate emissions of greenhouse gases (GHGs), specifically carbon dioxide (CO 2 ), from existing fossil fuel-fired power plants. The goal of the Rule, according to EPA, is to help protect human health and the environment from the impacts of climate change. The CPP has been one of the more singularly controversial environmental regulations ever promulgated, and the controversy is reflected in the enormous multi-party litigation over the Rule in the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Numerous petitions challenging the Rule have been consolidated under the caption West Virginia v. EPA . While the litigation is still ongoing at the circuit court level, an interlocutory—that is, mid-litigation—application to the Supreme Court resulted in a stay, or pause, of the Rule. This report provides legal background on the Rule, its Clean Air Act (CAA) framework under Section 111, and some of the main climate-related lawsuits that have preceded the present litigation over the CPP. It then gives an overview of the participants in the litigation, including Members of Congress, who have offered briefs in support of both sides. This report explains the major events in the litigation as of the date of publication, including the Supreme Court stay and the D.C. Circuit oral argument, and the expected schedule of events in the near term. It then presents condensed summaries of some of the main arguments on the merits. This report concludes with a brief look at parallel litigation in the D.C. Circuit that is challenging a related EPA regulation, which limits GHG emissions from new, modified, and reconstructed power plants. (B) Within one year after the inclusion of a category of stationary sources in a list under subparagraph (A), the Administrator shall publish proposed regulations, establishing Federal standards of performance [i.e., NSPSs] for new sources within such category....
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(d) (1) The Administrator shall prescribe regulations which shall establish a procedure similar to that provided by section [1]10 of this title [which provides for State Implementation Plans for NAAQS] under which 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 [1]08(a) …
[From this point, there is dispute in the litigation regarding how subparagraph (i) continues; the House-originated amendment, which appears in both the U.S. Code and the Statutes at Large , ends subparagraph (i) with " or emitted from a source category which is regulated under section [1]12 " while the Senate-originated amendment, which appears only in the Statutes at Large and not the U.S. Code , ends subparagraph (i) with " or section [1]12(b) " ] 
but 
(ii) to which a standard of performance under this section would apply if such existing source were a new source, and 
(B) provides for the implementation and enforcement of such standards of performance. EPA finalized Section 111(b) NSPSs for GHG emissions from new, modified, and reconstructed power plants at the same time as the Clean Power Plan. Thus, the stay briefing previewed some of the legal and factual arguments on both sides, including arguments relating to the scope of EPA's authority and the reasonableness of EPA's decisions. Circuit, who referred the actions to the full Court. Next Steps in West Virginia v. EPA

As noted above, oral argument was held on September 27, 2016.
On October 23, 2015, the U.S. Environmental Protection Agency (EPA) published its final Clean Power Plan rule (Rule) to regulate emissions of greenhouse gases (GHGs), specifically carbon dioxide (CO2), from existing fossil fuel-fired power plants. The aim of the Rule, according to EPA, is to help protect human health and the environment from the impacts of climate change. The Clean Power Plan would require states to submit plans to achieve state-specific CO2 goals reflecting emission performance rates or emission levels for predominantly coal- and gas-fired power plants, with a series of interim goals culminating in final goals by 2030.
The Clean Power Plan has been one of the more singularly controversial environmental regulations ever promulgated by EPA, and the controversy is reflected in the enormous multi-party litigation over the Rule ongoing in the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit). Numerous petitions challenging the Clean Power Plan have been consolidated into one case, West Virginia v. EPA. While the litigation is still ongoing at the circuit court level, an unusual mid-litigation application to the Supreme Court resulted in a stay of the Rule, meaning that the Rule does not have legal effect at least for the duration of the litigation. On September 27, 2016, the en banc (full court) D.C. Circuit heard oral argument for the case.
This report provides legal background on the Rule, its Clean Air Act (CAA) framework under Section 111, and climate-related lawsuits that have preceded the present litigation over the Clean Power Plan. It then gives an overview of the participants in the current litigation, including two groups of Members of Congress, who have offered briefs in support of both sides. This report highlights the major events in the litigation as of the date of publication, including the Supreme Court stay and oral argument, and the likely timetable of events in the near term.
Some of the main arguments on the merits are then briefly summarized and excerpted from court filings, including
the standard of review to apply to EPA's action; the scope of EPA's overall authority under CAA Section 111; whether Section 111 allows the Clean Power Plan's inclusion of generation-shifting, such as from coal-fired power plants to lower-emitting sources of electricity; the interpretation of a statutory exclusion in CAA Section 111 that cross-references CAA Section 112's regulation of hazardous air pollutants, particularly in light of the apparent enactment in 1990 of differing House and Senate amendments to the same cross-reference; constitutional arguments relating to federalism and separation of powers; record-based challenges to the achievability and reasonableness of the Rule; and arguments regarding rulemaking procedures.
This report concludes with a brief look at parallel litigation in the D.C. Circuit, consolidated as North Dakota v. EPA, which is challenging a related EPA regulation that imposes new source performance standards (NSPSs) limiting CO2 emissions from new, modified, and reconstructed fossil fuel-fired power plants.