In 2006, then-California Governor Arnold Schwarzenegger broke from Republican orthodoxy to sign several bills imposing caps on carbon emissions in California. Then-President George W. Bush opposed mandatory caps at a national level. Bush's decision not to regulate carbon dioxide as a pollutant was challenged in the Supreme Court by 12 states, with the court ruling against the Bush administration in 2007. Bush also publicly opposed ratification of the Kyoto Protocols which sought to limit greenhouse gas emissions and thereby combat climate change; his position was heavily criticized by climate scientists.