The Water Vapor Problem

The U.S. Environmental Protection Agency (EPA), in its ruling last week that overturned its 2009 Endangerment Finding on greenhouse gases (GHGs), argued that in light of Supreme Court judgments since 2009, it was reinterpreting the language of the Clean Air Act (CAA):

With this final action, we return to fundamental principles governing decision-making within our democratic system: “Agencies have only those powers given to them by Congress,” West Virginia v. EPA, 597 U.S. 697, 723 (2022), and “the scope of an agency’s own power” is determined not by deference to asserted expertise, but by “the best reading of the statute,” which is fixed at the time of enactment. Loper Bright Enters. v. Raimondo, 603 U.S. 369, 400-01 (2024). [emphasis added]

However, under the U.S. Constitution responsibility for determining the “best reading” of a statute lies exclusively with the judiciary, and not executive branch agencies.

EPA cited the Supreme Court’s judgment in Loper Bright, which also explained this central tenet of the U.S. Constitution:

[C]ourts may not defer to an agency interpretation of the law simply because a statute is ambiguous.

The notion that courts determine what the law is dates to Marbury vs. Madison in 1803:

It is emphatically the duty of the Judicial Department to say what the law is.

By engaging in judicial review outside its remit, the EPA may simply be begging to be sued, forcing the issue to the Supreme Court.1

It is of course conceivable that the Court might (a) decide that EPA was wrong procedurally to assume responsibility for judicial review of the CAA, but (b) substantively, the Court concurs with its de novo interpretation of the law in 2026, and thus overturns the 2008 Massachusetts vs. EPA ruling — which determined GHGs are pollutants and must be regulated by EPA, setting the stage for the 2009 Endangerment Finding.

It is particularly important that the 2008 Mass. vs EPA judgment explicitly rejected a de minimis argument — the notion that emissions from U.S. autos are too tiny to have a discernible effect on climate and thus are not worthy of regulation.

The court explained in Mass. vs. EPA:

A reduction in domestic emissions would slow the pace of global emissions increases, no matter what happens elsewhere. . . The risk of