The Southeastern Legal Foundation has filed suit, together with more than a dozen U.S. representatives and nearly two dozen associations, to challenge U.S. EPA's efforts to regulate carbon dioxide as a pollutant under the Clean Air Act (i.e., EPA's related "Endangerment Finding"), according to this opinion piece in the Washington Examiner.
A copy of the petition, and related materials, can be found here.
[Update: Texas is filing suit too, according to this article in the Houston Chronicle. (Moved up.) And more here from the NYT (note the "skeptic" pejoratives).]