Briefing has just concluded in a matter before the US Supreme Court involving challenges to the suite of greenhouse gas (GHG) cases decided by the US Court of Appeals for the District of Columbia Circuit in June 2012. In October 2013, the Supreme Court granted six petitions for writ of certiorari filed by industry and state petitioners on the following single issue:

Whether EPA [(the US Environmental Protection Agency)] permissibly determined that its regulation of greenhouse gas emissions from new motor vehicles triggered permitting requirements under the Clean Air Act for stationary sources that emit greenhouse gases.