As Oklahoma Attorney General, Pruitt sued the EPA at least 14 times. Regulated industry companies or trade associations who were financial donors to Pruitt's political causes were co-parties in 13 of these 14 cases. These cases included suing to block the anti-climate change Clean Power Plan four times, challenging mercury pollution limits twice, ozone pollution limits once, fighting the Cross-State Air Pollution Rule and the Clean Water Rule, as well as fighting regulations on methane emissions. Pruitt stated at his Senate confirmation hearing in January 2017 that the EPA has an "obligation" to regulate carbon dioxide in accordance with a 2007 Supreme Court case and 2009 EPA decision establishing carbon emissions as a threat to public health.