A three judge panel in the U.S. Court of Appeals in Washington has scraped the EPA’s Cross-State Air Pollution Rule which was issued on July 2011. The rule was the EPA’s attempt to address the problem of legally permitted emissions crossing state lines causing the downwind state to be out of compliance with the National Ambient Air Quality Standards. Two of the judges on the panel sided with more than three dozen challengers to the EPA’s rule which imposed caps on emissions for 27 states. The rule imposed a cap on sulfur dioxide which can lead to acid rain harmful to humans and ecosystems, and nitrogen oxide, a component of ground level ozone and a main ingredient of smog. The court ordered the agency to re-establish the 2005 Clean Air Interstate Rule until a viable replacement to the Cross-State Air Pollution Rule can be made.