On June 6, 2012, the D. C. Circuit Court of Appeals issued its much anticipated ruling on the combined challenges to EPA’s GHG Endangerment Finding, Timing Rule, Tailoring Rule and Light Duty Vehicle Tailpipe Emissions Rule. In a strongly worded opinion, the court found that EPA was “unambiguously correct” in its interpretation of the Clean Air Act provisions governing the Endangerment Finding and Tailpipe Rule and that none of the Petitioners had standing to challenge the Timing or Tailoring Rules. Thus, this is a total win for EPA and a total loss for the many state and industry Petitioners. The court echoed the Supreme Court’s holding in Massachusetts v. EPA, 549 U.S. 497 (2007) that EPA was required to regulate greenhouse gases unless it determined they do not contribute to climate change. In Massachusetts, the Supreme Court held that greenhouse gases “unambiguously” may be regulated as an “air pollutant.” The D.C. Circuit noted that the Clean Air Act PSD provision’s declaration of purpose section (42 USC 7470(1)) specifically references adverse effects on public “welfare” to include effects on weather and climate. With the statutory challenge out of the way, the court deferred to EPA on its factual findings, as most predicted it would. The court was unimpressed by the Petitioners’ “climate-gate” arguments, noting that the Intergovernmental Panel on Climate Change (IPCC) Report, which was heavily relied upon by EPA, was based on over 18,000 peer reviewed studies. Regarding the Timing and Tailoring Rules, many observers thought EPA was on thin statutory ice. But the court found it could not reach the merits of the Plaintiffs’ objections because none of the Plaintiffs had pointed to any “injury in fact” which these rules would cause to the Plaintiffs. The court noted that because the Timing and Tailoring Rules extended deadlines for compliance and increased the emission thresholds triggering GHG permitting, these rules “actually mitigate the Petitioners’ purported injuries.” As the Petitioners could point to no particularized, concrete harm to themselves, the court held they had no “standing” to challenge these rules, and thus the court had no jurisdiction to review those challenges. While an appeal is likely, if not certain, this opinion leaves little ground for reversal. This ruling has already become a political football, and theoretically Congress could amend the Clean Air Act to expressly deny EPA the authority to regulate GHG. However, many consider this unlikely as Congress has been highly reluctant to open up the Clean Air Act to amendment in recent years. Thus this opinion may mark the end of the long saga of ambiguity regarding how greenhouse gases will be regulated in the United States.