(The post was co-authored by Pamela Campos.)

Is a state responsible if it causes pollution in another state? The legal answer, going back more than a century, is yes.

In 1907, the State of Georgia sued Tennessee Copper Company for polluting its forests. In considering this suit, Supreme Court Justice Oliver Wendell Holmes stated “[i]t is a fair and reasonable demand on the part of a sovereign” in our federal system “that the air over its territory should not be polluted on a great scale … by the act of persons beyond its control.”

Flash forward 50 years, to the 1960s. Interstate air pollution was still a major problem – in this case, one of the key drivers for Congress passing the Clean Air Act to establish federal air quality legislation.

Another fifty years later, air pollution transported across state boundaries is a still a major issue. When Congress amended the Clean Air Act in 1990, areas in the northeast, among them New York City and Connecticut, were so polluted by emissions drifting in from out-of-state that they could not have met national air quality standards even if they had eliminated all air pollution from sources within their borders. Even today, EPA estimates that about 30% to 90% of smog and 50% to 90% of soot pollution in areas that are having trouble meeting the national, health-based air quality standards is caused by power plants, factories and other sources in states upwind.

EPA has been trying to fulfill its Congressional duty to protect downwind states from pollution that blows in on the wind for more than 15 years. It’s made progress, but there is much more to do, and most of the upwind polluting states haven’t taken even the first steps toward proposing their own solutions to the problem, as required by the Clean Air Act.

Unfortunately, when EPA stepped in to address the issue (which the Clean Air Act also requires) with its science-based and cost-effective Cross-State Air Pollution Rule, the D.C. Circuit Court of Appeals overturned the Rule.

The Cross-State Air Pollution Rule, also called the Transport Rule, would save up to 34,000 lives per year and protect the health of 240 million Americans by reducing harmful smokestack pollution from power plants. Overall, the Transport Rule would provide $110 to $280 billion per year in net health benefits.

Two of the judges on the D.C. Circuit concluded that the Transport Rule had to be set aside because EPA was supposed to tell the states what to do – that is, quantify precisely how much pollution they had to reduce – before expecting the states to submit their own plans. This was a strange decision for a couple of reasons. First, no one involved in the case had made this argument to the court, almost always a prerequisite before addressing complex administrative law issues. But even more strangely, the court’s decision ran roughshod over the plain terms of the statute that require states to prohibit interstate pollution irrespective of whether EPA identifies how states must combat this problem.

The D.C. Circuit also stepped right into the complex guts of EPA’s rule, creating a set of restrictions that, when applied to highly technical air pollution problems, simply don’t work.

Fortunately, on June 24, 2013, the U.S. Supreme Court agreed to review the D.C. Circuit’s decision, and will hear oral argument on December 10th. EDF joined the EPA, plus a host of other environmental and public-health organizations, states and cities, and power companies in filing opening briefs with the Supreme Court on September 4, asking the Court to overturn the D.C. Circuit’s decision. And on September 11, several more parties, representing a wide-range of interests and expertise, filed amicus (“friend of the Court”) briefs in support of EPA’s Transport Rule.

The Transport Rule is firmly anchored in science and law, and will ensure healthier and longer lives for 240 million Americans. We look forward to the high court hearing this compelling case for clean air.