Once the 111th Congress proved incapable of passing climate change legislation, the EPA began using its authority under the Clean Air Act to restrict greenhouse gas emissions from cars, power plants, and a variety of other mobile and stationary sources. In issuing regulations, however, the EPA opted to employ a regulatory track that limits it to cutting emissions to the extent economically and technologically feasible. That means, in practice, at a pace that sits well politically. Some environmental groups, however, want faster, more stringent regulation. Two such groups, the Center for Biological Diversity (CBD) and 350.org, have petitioned the EPA to invoke another regulatory track that would commit the agency to reducing greenhouse gases to the extent sufficient to protect public health and the environment, regardless of the cost or blowback from industry or voters. These provisions would require the EPA to set a National Ambient Air Quality Standard (NAAQS) for greenhouse gases based solely on considerations of health and environmental protection and to meet the NAAQS on a statutory timetable. The timetable comes in provisions that require states to adopt "implementation plans" to cut emissions to the extent necessary to achieve each NAAQS. Invoking these provisions would limit the EPA's ability to bob and weave to accommodate competing political pressures on greenhouse gases.