A federal court just handed down a ruling that could have far-reaching consequences for human health and the U.S. economy. Er, no, it wasn't the upcoming Supreme Court decision on Obamcare. But this case might end up proving just as significant.

No reprieve for you, smokestack. (AP Photo/John McConnico.)

On Tuesday, the U.S. Court of Appeals for the District of Columbia Circuit ruled that the Environmental Protection Agency (EPA) was "unambiguously correct" in moving ahead to set limits on greenhouse gas emissions from power plants and automobiles.

For now, that means the EPA can go about its business of tackling global-warming pollution. The challenges, by states like Virginia and Texas and by industry groups, have been rejected.

Let's recall the backstory: In 2007, the Supreme Court ruled that the EPA was required to regulate carbon-dioxide and other greenhouse gases under the Clean Air Act if it found that those gases posed a risk to human health (which, most scientists agree, they do). The EPA made that determination in 2009 and moved ahead with crafting new fuel-economy standards for cars and light trucks. This year, the agency also proposed limits on carbon pollution from new power plants — a rule that would essentially make it impossible to build coal-fired plants in the United States in the near term.

Dozens of states and industry groups (there were more than 60 lawsuits all told) had challenged the EPA's actions on three grounds. First, they argued that the EPA’s determination that greenhouse gases “threaten the health and welfare of current and future generations” was wrongly decided. Second, the groups argued against individual EPA rules, like the fuel-economy standards for cars and light trucks. The plaintiffs also argued that the agency's "Tailoring Rule" — in which the EPA limited its regulations to only the biggest power plants and facilities — was a misreading of the Clean Air Act.

The three-judge panel rejected all three of these arguments. On the first, the court ruled that the EPA had "substantial record evidence" that greenhouse gases are heating up the planet. The judges essentially deferred to the EPA's in-house expertise on this matter. “In the end, petitioners are asking us to re-weigh the scientific evidence before EPA and reach our own conclusion,” the panel wrote. “This is not our role.”

The court also found that the tailpipe rule for vehicles was "neither arbitrary nor capricious" and that industry groups lacked legal standing to challenge the Tailoring Rule. The EPA had devised the Tailoring Rule so that they wouldn't have to regulate every last source of carbon dioxide, down to individual buildings and barbecues. After all, that would be chaos. Some groups were trying to invalidate that rule (which does seem to contradict the plain language of the Clean Air Act) precisely in order to provoke chaos and force Congress to step in. But the court said that industry groups couldn't prove they'd suffered injury from an EPA move to limit its own powers. You can read the full opinion here.

So what does this all mean? For one, the EPA will finish up drafting standards requiring cars and light trucks to get a fleet-wide average fuel economy of 54.5 miles per gallon by 2025. And the agency can move forward with its rules limiting carbon pollution from new power plants. Next up: The agency has to decide whether to place carbon limits on existing power plants, as well as whether to regulate other major sources of pollution such as oil refineries or cement plants.

And these moves are arguably the biggest chunk of U.S. climate policy these days. With Congress not taking much interest in global warming these days, the EPA is likely to be the focal point of all action on carbon pollution for the foreseeable future.