On April 7, 2011, the United States Court of Appeals for the D.C. Circuit (“D.C. Circuit”) denied a petition by industry groups and the states of North Dakota and Texas to stay implementation and enforcement of new stringent sulfur dioxide (“SO2”) emissions standards pending the court’s review of those standards. The ruling will force states to proceed with plans for meeting a new SO2 limit of 75 parts per billion (ppb) averaged over an hour.  The old standard was a daily limit of 140 ppb and annual limit of 30 ppb.

A coalition of electric utilities, mining companies, and states are challenging the new SO2 National Ambient Air Quality Standards, arguing the new standards will be costly and time-consuming but unnecessary.  The D.C. Circuit ruling provides no indication as to where the court stands on the merits of the challenge; the ruling was a determination that petitioners did not satisfy the strict test of showing irreparable injury required to achieve a stay of the pending new limits during the court’s consideration of the lawsuit.