On Dec. 7, 2009, EPA formally issued its Greenhouse Gas Endangerment Finding. This finding clears the way for EPA to finalize its proposed greenhouse gas emissions standards for motor vehicles under Section 202(a) of the Clean Air Act. In its finding, EPA concludes that the atmospheric concentrations of six greenhouse gases, including CO2, threaten both the public health and welfare of current and future generations. In an attempt to limit the reach of this finding, EPA only found that the combined emissions of these greenhouse gases from new motor vehicles and new motor vehicle engines contribute to greenhouse gas air pollution. It ignored other sources of greenhouse gases. Challenging the endangerment finding as "backdoor climate regulations," Alaska Senator Lisa Murkowski announced on Dec. 14 that she would file a disapproval resolution in hopes of blocking EPA regulation of greenhouse gases under the Clean Air Act in favor of climate change legislation working its way through Congress.

Although all legal challenges to the endangerment findings must be filed within 60 days from Dec. 7, 2009, the National Cattlemen's Beef Association (NCBA) didn't wait that long. On Dec. 23, 2009, it filed a petition in the D.C. Circuit Court of Appeals challenging the "endangerment finding" rule, claiming that it's premature to issue this kind of finding, especially given the recent controversy surrounding the scientific validity of alleged human contributions to climate change.