Climate change has affected many states and localities in the United States. The city and county of Boulder, Colorado, have not been spared: They have incurred property damage and spent millions of dollars protecting their residents from the impacts of global warming. Seeking compensation for these injuries, Boulder sued several oil and gas companies in Colorado state court, bringing nuisance, trespass, and other state tort law claims based on the companies’ knowing contributions to climate change and their misleading of the public about its dangers. The companies moved to dismiss, arguing among other things that the structure of the Constitution forbids the application of Colorado state law in cases involving interstate pollution. The district court rejected that argument, and the Colorado Supreme Court affirmed. The companies then successfully petitioned the United States Supreme Court for review.

In August 2026, the Constitutional Accountability Center filed an amicus brief in support of Boulder. Our brief makes two principal points.

First, the brief explains that states have long had the authority to remedy harms that their residents experience within the state, even when the conduct causing those harms occurred beyond state borders. The Framers’ original understanding of state power, early legislative practice, and Supreme Court precedent all confirm that state law can redress—and indeed, has redressed—harms caused by out-of-state actors. Our brief also demonstrates the weaknesses of the arguments to the contrary that the energy companies and the Trump administration are making in this case. In particular, the brief shows that the Trump administration’s narrow view of when state law can apply to out-of-state activities is unsound. None of the authorities the administration cites even remotely supports the novel constitutional rule it has devised. Nor do the text and history of the Constitution lend any weight to its argument.

Second, our brief explains that even though the Supreme Court has applied federal law to interstate-pollution disputes in prior cases, that precedent does not foreclose the application of state law in this case. In the early twentieth century, the Court applied judge-made federal common law in certain pollution cases because they involved states who participated as parties and invoked the Court’s “original” jurisdiction. That jurisdiction—which differs from appellate review of lower-court decisions—exists to provide a neutral forum for resolving interstate conflicts that might otherwise lead to aggression between states. For that reason, only federal law, not any individual state’s own law, had to apply in those disputes. But Boulder’s case, brought in state court and not involving any state as a party, is far afield from those precedents. Our brief also clarifies that the Supreme Court’s more recent water-pollution cases applied federal law because of congressional legislation and its implications, not because the structure of the Constitution somehow precluded applying state law.

Simply put, the Supreme Court has never held that the Constitution forbids state law from providing remedies for injuries experienced within a state as a result of interstate pollution. It should not do so now.