In 2003 the EPA determined that they were not authorized to regulate greenhouse gasses. In 2007, by a 5-4 decision, the Supreme Court determined that the Clean Air Act does in fact authorize federal regulation of greenhouse gases if determined as pollutants and therefore the EPA as the regulatory body empowered with the task and must make a ruling on CO2.
http://www.supremecourt.gov/opinions/06pdf/05-1120.pdf


>I'm going by memory here but wasn't there a case a few years back that declared carbon dioxide a hazardous compound? I am scratching my head over this one.
>
>>Nearly fell out of my chair when I heard this.
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>>The justices of the United States Supreme Court this week became the world’s most august global warming sceptics. Not by virtue of their legal reasoning – the global warming case they decided turned on a technical legal issue — but in their surprising commentary. Global warming is by no means a settled issue, they made clear, suggesting it would be foolhardy to assume it was.
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>>“The court, we caution, endorses no particular view of the complicated issues related to carbon-dioxide emissions and climate change,” reads the 8-0 decision, delivered by the court’s acclaimed liberal, Justice Ruth Bader Ginsburg.
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>>The court decision noted that the Environmental Protection Agency itself had “Acknowledg[ed] that not all scientists agreed on the causes and consequences of the rise in global temperatures,” before suggesting readers consult “views opposing” the conventional wisdom. Specifically, the justices’ recommended reading was a superb profile of Princeton’s Freeman Dyson, perhaps America’s most respected scientist, written in the New York Times Magazine, March 29, 2009.
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>>Freeman, an unabashed skeptic, believes that carbon dioxide, rather than being harmful, is both necessary and desirable, arguing that “increases in atmospheric carbon dioxide produce many beneficial effects upon the natural plant and animal environments of the Earth.”
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>>Somewhat in the same vein, Justice Ginsburg notes carbon dioxide is necessary and ubiquitous, and thus shouldn’t be the target of indiscriminate attacks. “After all, we each emit carbon dioxide merely by breathing,” she notes, repeating a point that Dyson couldn’t have said better himself.
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>>http://opinion.financialpost.com/2011/06/23/lawrence-solomon-supreme-skeptics/
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>>I'm still rubbing my eyes. THAT was written by Justice Ginsburg?
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>>The 1st quote is from her 2nd footnote.
>>Full opinion here: http://www.supremecourt.gov/opinions/10pdf/10-174.pdf