Yes they did, about 8 months back. It's classified a pollutant and the Supreme Court said The Clean Air Act dictated the EPA had to treat it as such. Here's the article about this Supreme court decision ruling, I've only provided the pertinent parts pertaining to your question, a link is provided below to the entire article to look at as well.
Justices Rule Against Bush Administration on Emissions
By LINDA GREENHOUSE
Published: April 2, 2007
WASHINGTON, April 2 — In one of its most important environmental decisions in years, the Supreme Court ruled today that the Environmental Protection Agency has the authority to regulate heat-trapping gases in automobile emissions.
The court further ruled that the agency cannot sidestep its authority to regulate the greenhouse gases that contribute to global climate change unless it can provide a scientific basis for its refusal.
The 5-to-4 decision was a strong rebuke to the Bush administration, which has maintained that it does not have the right to regulate carbon dioxide and other greenhouse gases under the Clean Air Act, and even if it did, it would not use the authority. The ruling does not force the Environmental Protection Agency to regulate auto emissions, but it would almost certainly face further legal action if it fails to do so.
Writing for the majority, Justice John Paul Stevens said that the only way the agency can “avoid taking further action” now is “if it determines that greenhouse gases do not contribute to climate change” or provides a good explanation why it cannot or will not find out whether they do.Beyond the specific context for this case — so-called “tailpipe emissions” from cars and trucks, which account for about one-fourth of the country’s total greenhouse-gas emissions — the decision is highly likely to have a broader impact on the debate over government efforts to address global warming.
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Following its discussion of standing, the majority made short work of the agency’s threshold argument that the Clean Air Act simply did not authorize it [the E.P.A.] to regulate greenhouse gases because carbon dioxide and the other gases were not “air pollutants” within the meaning of the law.
“The statutory text forecloses E.P.A.’s reading,” Justice Stevens said, adding that “greenhouse gases fit well within the Clean Air Act’s capacious definition of air pollutant.”
The justices in the majority also indicated that they were persuaded by the existing evidence of the impact of automobile emissions on the environment.
The agency itself “does not dispute the existence of a causal connection between man-made gas emissions and global warming,” Justice Stevens noted, adding that “judged by any standard, U.S. motor-vehicle emissions make a meaningful contribution to greenhouse gas concentrations.”
(entire article at link for my source)
