On the surface, Suncor Energy v. County Commissioners of Boulder County at the Supreme Court looks like a pure climate-change suit—the City of Boulder’s attempt to use Colorado tort law to extract damages from energy companies for their alleged contributions to global warming.
But the case is about far more than it appears, at least according to three amicus briefs filed this week in support of the petitioners, each of which deserves special attention.
The briefs, by Save Our States, Consumers’ Research, and Tennessee Attorney General Jonathan Skrmetti, are worth reading, as they cut through the noise and each in their own way ask a core constitutional question: whether our constitutional design lets one state govern conduct in another state, regardless of whether the topic is climate change or anything else.
The Suncor amicus briefs speak in different words—two emphasize territorial jurisdiction, one focuses on territorial sovereignty—but they converge on the same point: the structure of the Constitution contains a limit on extraterritorial overreach by one state into the others, as the Founders understood the states to be coequal sovereigns whose authority stops at their borders. The Constitution preserved that status, and although the states ceded certain enumerated powers to the federal government, they retained the right to govern within their own spheres, but not beyond.
Consumers’ Research, represented by Tyler Green, a standout Supreme Court advocate (and a fellow former clerk to Justice Thomas), explained this extraterritorial limitation in its brief as the doctrine of territorial jurisdiction. The central claim in the brief is simple: a state’s lawmaking power stops at its border. That limit was drawn from the law of nations long before the Founding and carried forward into our constitutional order.
The brief marshals sources from the Founding era and early Republic, including Vattel’s Law of Nations and Justice Story’s treatise on conflicts. Justice Story put it plainly: “no state or nation can, by its laws, directly affect, or bind property out of its own territory.” The brief traces this principle across the Constitution’s Full Faith and Credit, Privileges and Immunities, Export-Import, and Due Process Clauses, and through more than a century of cases holding that interstate environmental disputes cannot be governed by the law of any single state.
The Save Our States brief—authored by Michael McGinley, a Supreme Court regular and former clerk to Justice Alito and then-Judge Gorsuch—adds a lot to the historical case for the extraterritoriality principle. The brief drives home that “extraterritorial regulation would have been unthinkable in the eighteenth century.” Under the law of nations as understood at the Founding, “the jurisdiction of the nation within its own territory is necessarily exclusive and absolute,” as Chief Justice Marshall put it in The Schooner Exchange v. McFaddon (1812). That principle was baked into colonial practice from the start. The New England colonies, for instance, agreed in 1643 that each “shall have peculiar jurisdiction and government within their limits.”
The Constitution didn’t loosen those limits—if anything, it tightened them. Under the Articles of Confederation, the states “aggrandize[d] themselves at the expense of their neighbors” (Hamilton, Federalist 6). The Constitution resolved this by stripping states of “the power of aggressive operation against each other.” The Supreme Court enforced that limit from the start. Chief Justice Marshall declared “without hesitation” in United States v. Bevans (1818) that “the jurisdiction of a state is co-extensive with its territory.” In Rhode Island v. Massachusetts (1838), the Court held that no state can “have any right beyond its territorial boundary.” The principle that emerges from the historical record is clear: under our Constitution, each state governs within its borders, but not one inch beyond.
The State of Tennessee, in a brief signed by Attorney General Jonathan Skrmetti and Solicitor General Matthew Rice (another former clerk to Justice Thomas), offers a related framing: why territorial sovereignty requires reversal. Tennessee explains that territorial sovereignty is a preexisting attribute of statehood, recognized by the law of nations and preserved by the states at ratification. Building upon that foundation, the Constitution created a federal government of limited, enumerated powers. Apart from that limited delegation, the states were left largely as the Framers found them: independent sovereigns within their borders.
As Tennessee points out, “[t]he Constitution’s text recognizes the continued existence of the States’ territorial sovereignty.” From the Tenth Amendment (which explicitly “reserve[s]” to the states “respectively” all powers not “delegated” to the federal government) to the Full Faith and Credit Clause (which requires states to recognize judgments issued by the courts of sister states), “the Constitutional text reinforces rather than supplants” states’ territorial sovereignty.
Tennessee’s brief also offers the most vivid picture of what is at stake. Under the Colorado Supreme Court’s reasoning, “any conduct that impacts the global climate in ways that are felt in Colorado—no matter how remote—must comply with Colorado tort law.” Tennesseans drive gas-powered cars to work. West Virginians heat their homes with coal-fired electricity. Texas ranchers raise cattle that emit methane. Colorado, on the decision below, claims a regulatory interest in all of it. As Colorado Supreme Court Justice Carlos Samour, Jr. explained in dissent, that decision gives Boulder “the green light to act as its own republic.”
That can’t be right—and it isn’t.
Together, these briefs shed light on the bedrock constitutional arguments likely to shape how the justices resolve the case. The Founders understood the states to be coequal sovereigns whose authority stops at their borders. The Constitution preserved that status. Although the states ceded certain enumerated powers to the federal government, they retained the right to govern within their own spheres—but not beyond.
Suncor is about far more than one municipality’s aggressive climate litigation. A clear repudiation of Boulder’s overreach would have ripple effects wherever politicians attempt to impose blue-state policies nationwide through litigation. The pattern is familiar by now: a single state or municipality, frustrated by Congress, deploys state law to dictate national policy on energy, firearms, agriculture, or consumer products. A decision reaffirming states’ equal sovereignty and territorially limited jurisdiction would stop those unconstitutional efforts in their tracks.
Given its far-reaching implications, Suncor is one to watch closely next term. The justices will have a chance to vindicate an overlooked but essential tenet of our constitutional order: that the states stand as equals, and no single state, much less a single city, may govern the nation.