Following up on this article, Ryan J. Walsh & Michael A. Fragoso have a new post: Three Threads from the Suncor Argument? (9 Notre Dame J.L., Ethics & Pub. Pol’y: In Limine 1 (2026)). From the introduction:
We found three exchanges at Monday’s argument in Suncor Energy (U.S.A.) v. County Commissioners of Boulder County particularly interesting and address them further here: (1) Since the defendants are producers rather than emitters, where is the “source State” whose law Ouellette preserved? (2) What does EPA’s current disclaimer of authority over greenhouse gases do to AEP? (3) If Congress carved greenhouse gases out of the Clean Air Act (CAA) altogether, would it follow that “nobody can sue at all?”
All three questions hover around propositions that we defended last month: A State’s law has always stopped at its border, the Constitution gave States no means to change that rule, and the federal common law of interstate pollution exists because of it.
RELATED: At SCOTUSblog, John Shu: The Constitution’s structure should decide Suncor. From the core of the argument:
The defendant energy companies argued that the Constitution’s structure bars one state’s law from governing claims about interstate and international emissions on the basis that one state may not impose its policies on other states and state sovereignty is subject to inherent territorial limits; and because regulating or negotiating international emissions implicates the federal government’s exclusive foreign affairs power.
Boulder responded that because the 10th Amendment reserves the “powers not delegated to the United States by the Constitution, nor prohibited by it to the States,” it permits states to do anything that the Constitution does not explicitly forbid. Under Boulder’s framing, the Constitution “bestows only limited powers on the federal government,” and “all other legislative power is reserved for the States.” From that premise, Boulder argues that there can be no preemption without a textual hook in the Constitution or a federal statute.
But the 10th Amendment does not specify what the Constitution prohibits and it does not address the inherent limits on state sovereignty that predated the Constitution and which it preserved. Before the union, a state injured by a neighboring state’s pollution could respond only through diplomacy or force. The 1907 case of Georgia v. Tennessee Copper held that the states gave up those options when they entered the union and in return received federal forums which applied federal law. The 1907 case of Kansas v. Colorado called “equality of right” the “cardinal rule” governing the states’ relations with one another, under which each state “stands on the same level with all the rest” and “can impose its own legislation on no one of the others.” Boulder’s state tort claim runs afoul of that principle. Its complaint seeks billions of dollars for alleged past and future harms stemming from energy companies’ worldwide activities. A judgment in Boulder’s favor thus necessarily would influence and/or restrict the companies’ operations in other states far beyond Colorado’s borders, regardless of what those states’ policies may be.
The answer is even clearer for international emissions. “No state can say, that it has reserved, what it never possessed,” the court wrote in 1995’s U.S. Term Limits, Inc. v. Thornton, quoting Justice Joseph Story’s Commentaries on the Constitution of the United States. More recently, in 2007’s Massachusetts v. EPA, the court observed that Massachusetts “cannot negotiate an emissions treaty with China or India,” because those “sovereign prerogatives are now lodged in the Federal Government.” It would seem obvious that a state which cannot negotiate over foreign emissions also cannot allocate responsibility between alleged foreign and domestic emitters through a jury verdict.
I share the intuition that what Colorado is trying to do in Suncor goes beyond the proper power of a state. But I’m nervous about arguments that appeal to federal common law or dormant foreign affairs power, both of which I’m highly skeptical of as an originalist matter– see here (federal common law) and here (dormant foreign affairs power).
Posted at 6:03 AM