Environmentalists often accused the Bush Administration of undermining environmental regulations. But in the area of air pollution, one administration cleanup attempt was stymied by the courts.

The Clean Air Interstate Rule (CAIR) of 2005, established under the Clean Air Act, created a regional cap and trade program in 28 eastern states and the District of Columbia. It was aimed at reducing smog-forming and soot-producing sulfur dioxide (SO2) and nitrogen oxide (NOX) emissions from coal-fired electric plants, with the intention of cutting pollution around the plants and in downwind states, where the emissions led to ozone and fine particulate matter pollution.