Despite an urgent plea from a united front of business advocates, the U.S. Supreme Court last week declined to review a case that could have put an end to state common-law litigation against companies for excess air pollution.

In a little-noticed action June 2, the court denied review in GenOn Power Midwest v. Bell, sweeping aside a bevy of briefs highlighting the “critically important” issue, in the words of the U.S. Chamber of Commerce.