From the blog:
"Issue: Whether, in 42 U.S.C. § 7411(d), an ancillary provision of the Clean Air Act, Congress constitutionally authorized the Environmental Protection Agency to issue significant rules — including those capable of reshaping the nation’s electricity grids and unilaterally decarbonizing virtually any sector of the economy — without any limits on what the agency can require so long as it considers cost, nonair impacts and energy requirements."