On Friday, October 16, 2009, the United States Court of Appeals for the Fifth Circuit held that the complaint of the class action plaintiffs in the case of Ned Comer v. Murphy Oil USA, et. al., Case No. 07-60756, could proceed. Reversing the lower federal court, the court ruled that the plaintiffs, residents and owners of land and property along the Mississippi Gulf Coast had standing to assert their claims that the defendants' operation of energy, fossil fuels and chemical industries in the United States caused the emission of greenhouse gases, which contributed to global warming, which in turn caused a rise in sea levels and added to the ferocity of Hurricane Katrina, which destroyed their property. Moreover, the court held that this complaint did not assert a non-justiciable political question.

The plaintiffs sought compensatory and punitive damages based on Mississippi common law precedent and the provisions of the Mississippi Constitution, and they argued they had standing to litigate these claims based on the 2007 decision of the United States Supreme Court in Massachusetts v. EPA. The Court held that the states had standing to seek review of a decision by the EPA not to regulate carbon dioxide emissions, and that CO2 is a pollutant as defined by the Clean Air Act, and could be regulated as such provided that EPA makes the appropriate finding that its emissions are an "endangerment" under the law, and there was a plausible link between man-made emissions of greenhouse gases and global warming. While allowing the claims based on private and public nuisance, negligence and trespass to continue, the Appeals Court dismissed the claims based on allegations of unjust enrichment, fraudulent misrepresentation and civil conspiracy.

The Appeals Court not only overturned the brief dismissal order issued by the U.S. District Court for the Southern District of Mississippi, but also harshly criticized the lower court decisions in California v. General Motors Corporation and the first American Electric Power case decided in the Southern District of New York.