State carbon policies to control climate warming and our energy future are under legal attack. A successful barrage of litigation now invokes the dormant Commerce Clause and the Federal Power Act as interpreted through the Filed Rate Doctrine, as well as the Supremacy Clause of the U.S. Constitution, to challenge the legal validity and sustainability of these state carbon-based laws. California and other states have survived these legal challenges sparingly, and then often only by prevailing with procedural defenses that dismiss the case before a decision on the legal merits of their state energy regulation. This Article examines and analyzes the multiple legal dimensions of challenges on carbon control and sustainable energy in a constellation of states, comparing them to California’s particular legal challenges. The Constitution is not changeable by simple legislation; its requirements and restrictions endure, and state action on energy can be ruled unconstitutional. The now-forming precedent will construct and limit the U.S. carbon-control future as states labor to achieve a legally sustainable economy. This Article navigates these recent challenges to state carbon control and sustainable energy statutory and regulatory law. How the judiciary is resolving each challenge, and the precedent created, will chart the future of U.S. sustainable energy policy.