The scientific, economic, and political questions surrounding climate change have long been with us. This report focuses instead on a relative newcomer: the legal debate. Though the first court decision related to climate change appeared 19 years ago, the quantity of such litigation has mushroomed in recent years. One observer counts 118 lawsuits and petitions for government action filed on climate change issues through the end of 2008—41 lawsuits filed in 2007 alone. Representatives of some suing organizations and states acknowledge that a prime cause for this litigation surge is the inaction of Congress and the executive branch during the George W. Bush Administration with regard to mandatory constraints on greenhouse gas (GHG) emissions, and their perception that litigation might help to prompt such action. Early signs are that the pace of new filings during the Obama Administration may be tapering off. The principal court cases, decided and pending, arise in eight contexts—a number that continues to grow. First and most important is the Clean Air Act (CAA). In April, 2007, the Supreme Court held in Massachusetts v. EPA that the U.S. Environmental Protection Agency (EPA) has authority under the CAA to regulate greenhouse gas emissions from new motor vehicles. The second context for climate change litigation is the federal wildlife statutes, raising the issue of whether statutes like the Endangered Species Act can be used to limit GHG emissions based on their contribution to climate-climate-related alterations of wildlife habitat. Third is the federal energy statutes, such as the Energy Policy and Conservation Act and Outer Continental Shelf Lands Act, which also raise questions as to whether climate change impacts must be considered in their spheres. The fourth context for litigation is federal information statutes such as the National Environmental Policy Act, exploring the extent to which they can be used to compel government analysis of and dissemination of information about climate change. Fifth is common law tort theories such as nuisance and whether they be used successfully by state and private plaintiffs to force cutbacks in GHG emissions, or payment of damages? Sixth is federal preemption of state regulation of GHG emissions. This category breaks down into efforts by states and environmentalists to reverse EPA's refusal to waive Clean Air Act preemption, and auto industry efforts to impose preemption under non-Clean Air Act theories, such as the "CAFE standards" under the Energy Policy and Conservation Act. Seventh, chiefly with respect to coal-fired power plants, is state utilities laws. And eighth is whether general liability insurance policies cover harms and liabilities caused by climate change. Sections I through VIII of this report address these eight areas of litigation in turn. Most known cases, decided and pending, are mentioned—omitted cases are those that raise climate change issues in only the most marginal way or only implicitly, and some state cases. Looking beyond the domestic lawsuits, Section IX surveys international law arguments that might be used to induce GHG emission reductions from the United States and other countries that are major GHG emitters, and the few international law claims filed against the United States to date. Finally, Section X offers overall comments. Aware that prospects for Senate approval of the Kyoto Protocol were dubious, some Members of Congress became concerned in the late 1990s that the Clinton Administration EPA might seek to regulate GHG emissions in the absence of approval, under either of two claimed authorities. One authority would derive from an argument that even prior to ratification, the Protocol provided some sort of legal basis for emissions restrictions, perhaps citing past treaties signed by the United States that were provisionally implemented prior to going into effect. This possibility provoked a series of enactments barring EPA's use of appropriated funds to implement the Kyoto Protocol in the absence of approval and ratification. The rest of this section deals with the second claim of possible authority: regulating GHG emissions independently of the Protocol, under the CAA. This authority has now been confirmed by the Supreme Court, at least as to mobile sources; nonetheless, this report retains from earlier versions the historical evolution of the issue. In 1998, an EPA General Counsel memorandum concluded that CO 2 satisfies the CAA definition of "air pollutant," but that this conclusion is only the first step. Before EPA can regulate CO 2 emissions, the memorandum went on, it must further conclude that CO 2 meets criteria in other CAA provisions requiring the agency to determine that the substance poses harm to public health, welfare, or the environment. This next step EPA declined to take. At a House hearing in 1999, a panel of legal experts argued the question of EPA's authority to regulate CO 2 under the CAA. A new EPA General Counsel endorsed his predecessor's analysis in the 1998 memorandum, but just as his predecessor, stressed that the EPA's legal analysis was "largely theoretical" since "EPA currently has no plans to regulate carbon dioxide...." This hands-off position was prompted in part by strong congressional opposition based on uncertainties as to the economic impact of regulating a pollutant as widespread as CO 2 . In addition, some in Congress argued that CAA implementation of a CO 2 standard was barred by the aforementioned enactments (appropriation riders) prohibiting implementation of the Kyoto Protocol. The EPA General Counsel opinion that "air pollutant" includes GHGs held sway until 2003, when that office reversed itself in the context of a petition asking the agency to regulate GHG emissions from mobile sources. This story picks up below ("Mobile Sources of GHG Emissions"). The earliest lawsuit in this category, now dismissed, sought to have EPA promulgate national ambient air quality standards for CO 2 . In Massachusetts v. Whitman , filed in 2003, three Northeast states (MA, CT, ME) sought to force EPA to list CO 2 as a "criteria pollutant" under the CAA. They argued that on various occasions, EPA had indicated its belief that CO 2 emissions contribute to climate change. These EPA statements constituted, in the words of CAA section 108, a "judgment [that GHG emissions] cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare" and "result[] from numerous or diverse mobile or stationary sources." These prerequisites being satisfied, the suit argued, section 108 requires EPA to add CO 2 to its list of "criteria pollutants," then proceed under section 109 to develop national ambient air quality standards for CO 2 . On September 3, 2003, a few days after EPA's denial of a petition asking the agency to regulate GHG emissions from motor vehicles, the plaintiff states voluntarily dismissed this suit, reportedly so as to transfer their energies to a suit challenging the petition denial (leading to the Supreme Court's Massachusetts v. EPA decision). The remaining suits in this category are all active today. Each one seeks EPA regulation of GHG emissions through new source performance standards (NSPSs) under the CAA. In most of these cases, regulation of GHGs is not the primary issue. Nonetheless, it should be noted that they will be litigated in the shadow of the Supreme Court ruling in Massachusetts v. EPA holding that EPA has authority under the CAA to regulate GHGs from mobile sources. The burning question is how that ruling will affect EPA regulation of stationary-source GHG emissions. The first NSPS suit was New York v. EPA , an effort to compel EPA to issue a NSPS for CO 2 from steam generating units. New York began with an EPA proposal to revise its NSPSs for electric utility and other steam-generating units. Some commenters on the proposed rule argued that EPA must, in addition to the revisions proposed, set NSPSs for GHGs emitted from steam generating units. The commenters pointed to CAA section 111's command that EPA promulgate NSPSs to address emissions from new stationary sources that "cause[], or contribute[] significantly to, air pollution which may reasonably be anticipated to endanger public health or welfare." In promulgating its final rule in February, 2006, however, EPA rejected this demand, saying (it being pre- Massachusetts v. EPA ) that the agency lacked authority to set NSPSs for GHGs. Review of the final rule was sought in the D.C. Circuit. In 2006, the court severed the portion of the case dealing with regulation of GHGs, titling it New York v. EPA . In 2007, a few months after the Supreme Court decision in Massachusetts v. EPA , this severed case was remanded to EPA for further proceedings in light of that decision (this section infra ) . Two other NSPS suits concern oil and natural gas—the production side in one suit; the refining side in the other. As to production, plaintiffs in WildEarth Guardians v. Johnson , No. 1:09 CV 00089 (D.D.C. filed January 14, 2009), invoke the CAA citizen suit provision to force EPA performance of alleged nondiscretionary duties under both the NSPS and National Emission Standards for Hazardous Air Pollutants provisions of the act. The complaint notes CO 2 , and particularly methane, as GHG pollutants of concern. Since neither of these pollutants is listed as a hazardous air pollutant, it may be surmised that the sole portion of the lawsuit pertinent to climate change is the NSPS claim. That claim alleges EPA's failure to review and revise the NSPS for the Crude Oil and Natural Gas Production category since 1985, despite the CAA requirement that NSPSs be reviewed, and if appropriate revised, every eight years. As for oil and gas refining, New York and 11 other states (CA, CT, DE, ME, MA, NH, NM, OR, RI, VT, and WA) filed a petition for review in 2008 challenging EPA's revisions that year of its existing NSPS for petroleum refineries. Petitioners' argument in New York v. EPA , No. 08-1279 (D.C. Cir.