On July 22, 2002, over the strenuous opposition of the United Auto Workers (UAW) and the auto industry, Governor Gray Davis of California signs a stringent law regulating emissions from automobiles.

The U.S. Congress passed the first national fuel economy standards, known as Corporate Average Fuel Economy (CAFE) standards, in 1975, in the wake of the 1973 oil embargo.

The standards sought to control emissions of so-called “greenhouse gases” (such as carbon dioxide) from cars and light trucks that contribute to global warming, or the gradual increase in the temperature of the earth’s atmosphere. Automakers have historically resisted increases in these standards, as stricter standards usually require an overhaul of their production methods to make cleaner and more fuel-efficient vehicles.

California–which represents 10 percent of the nation’s automobile market and is known for its struggles with air pollution–took the lead early in setting stricter fuel emissions standards than the federal government’s. Assembly Bill (AB) 1493, which Davis signed into law in July 2002, was the first law in the nation to address the greenhouse gases emitted in automobile exhaust. The law required the California Air Resources Board (CARB) to regulate greenhouse gases under the state’s motor vehicle program and gave automakers until the 2009 model year to produce cars and light trucks that would collectively emit 22 percent fewer greenhouse gases by 2012 and 30 percent fewer by 2016.

Despite his well-documented enthusiasm for the Hummer, a sport-utility-vehicle (SUV) known for its prodigious size (and prodigious emission of greenhouse gases), Davis’ Republican successor, Governor Arnold Schwarzenegger, sought to uphold AB 1493 against continuous challenges from the auto industry and the presidential administration of George W. Bush. Democrat Barack Obama’s election as president in 2008 turned the tide in California’s favor: In January 2009, Obama directed the Environmental Protection Agency (EPA) to reverse an earlier decision and give California (by then joined by 13 other states) the right to adopt tougher auto emissions standards. That May, Obama announced plans to bring the entire nation up to California’s proposed standard, which would make cars nationwide roughly 30 percent cleaner and more fuel-efficient by 2016.