Under the Clean Air Act, EPA is in the process of regulating greenhouse gas emissions from industrial and other "stationary" (non-mobile) sources. EPA determined that compliance for smaller sources of greenhouse gases should be phased in. Accordingly, EPA adopted a so-called "tailoring" rule, a regulation that sets forth which facilities will be required to obtain permits and implement pollution controls for greenhouse gas emissions and in what time-frame. The Attorney General filed a comment letter supporting the draft tailoring rule. Read the letter, pdf. EPA adopted the final rule in May, 2010. Read the rule. Numerous industry groups filed suit challenging the rule. The California Attorney General, together with twelve other states and environmental groups, intervened in the case to support EPA's rule. On June 26, 2012, the Court of Appeals for the D.C. Circuit upheld EPA’s tailoring rule, as well as other regulatory actions that are essential to EPA’s regulation of greenhouse gases emissions from stationary sources. Read the decision, pdf. On October 15, 2013, the Supreme Court declined industry’s request to review the tailoring rule.