Since we've been talking about global warming on this site a bit, I thought I'd link to the Supreme Court's opinion today (written by my former boss, and joined by Justices Kennedy, Souter, Ginsburg and Breyer) in Massachusetts v. EPA. The Court held that the Bush Administration was wrong to insist that it lacked the authority under the Clean Air Act to regulate CO2 emissions. While the Court did not mandate that the EPA begin to regulate CO2, it did order the EPA to determine whether CO2 contributes to climate change or to provide a reasonable explanation why it will not exercise its discretion to regulate CO2.

For those interested in the broader issue of the Bush Administration's expansive theories of executive power, the Court also provided us with this little gem in the course of rejecting the EPA's argument that regulating CO2 might "impair the President's ability to engotiate with 'key developing nations' to reduce emissions": "[W]hile the President has broad authority in foreign affairs," the Court replied, "that authority does not extend to refusal to execute domestic laws."