Buschbacher Probes Prof. Adler’s Amicus Brief in Suncor: Did He Align with the Wrong Side?

Originally, the federal rule was federal common law—or what was often described as the general law. Erie Railroad Co. v. Tompkins did not do away with this body of law, since rules concerning “air and water in their ambient or interstate aspects,” Illinois v. City of Milwaukee, 406 U.S. 91, 103 (1972), are “matters essentially of federal character,” United States v. Standard Oil Co. of Cal., 332 U.S. 301, 307 (1947).

However, the governing federal framework shifted in the 1970s when Congress enacted the central environmental statutes we rely on today: the Clean Air Act, the Clean Water Act, and the like. These statutes not only displaced federal common law; they also nationalized pollution policy in a new way. Rather than establishing a single nationwide command-and-control regime, the Clean Air Act and Clean Water Act largely created a system of “cooperative federalism” that pressures states to regulate more stringently through funding mechanisms and penalties designed to meet federal pollution-control benchmarks set by the EPA.

Prof. Adler portrays this as Congress preserving a broad degree of state discretion. That portrayal glosses over the historical reality in the realm of traditional state sovereignty—while the Clean Air Act did push much of American industry overseas, it did not arbitrarily sweep away all state regulatory authority. In many areas, Congress did allow states some flexibility in determining how best to reduce in-state pollution. As Adler notes, there are exceptions where Congress did remove in-state regulatory power to avoid a patchwork of conflicting state rules—such as motor-vehicle emissions—but, by and large, Congress did not overturn the preexisting balance of federal and state power over emissions regulation.

The challenge Boulder County faces is that under that prior balance, states had no authority to apply their own law to emissions originating outside their borders, because that domain had always been governed by federal common law. That point undercuts Boulder County’s position, since nothing in the Clean Air Act purports to grant states a new power to impose their own state laws on emissions that start outside their borders, much less to do so with the “exceedingly clear language” that would be required if Congress intended to radically reshape the federal-state balance.” Sackett v. EPA, 598 U.S. 651, 679 (2023) (cleaned up). Indeed, the various provisions of the Clean Air Act that explicitly address interstate and international emissions all presume the continued existence of traditional territorial limits on governmental authority. See 42 U.S.C. §§ 7402, 7410(a)(2)(D), 7415, 7426, 7506a. Prof. Adler does not address these provisions.

Where “Climate Nuisance” Fits In. This leads to my first disagreement with Prof. Adler. He suggests that climate-related nuisance and trespass claims would have been governed by state law prior to the Clean Air Act, and thus are within the broad range of state powers that statute purportedly “preserved.” I remain skeptical. Boulder County’s lawsuit is largely about conduct well outside Colorado, and the Suncor complaint does not target emissions from particular facilities causing specific harm; instead, it seeks to hold companies liable for broad, undifferentiated, and future harms that originate globally from widespread emissions.

With apologies to Prof. Adler, this bears little resemblance to a claim about a nearby “city whose sewer breached into the state line.” Adler Br. at 6 (describing Carmichael v. City of Texarkana, 94 F. 561 (C.C.W.D. Ark. 1899)). In fact, Carmichael shows how distinct Boulder County’s theories are from traditional nuisance claims. Mr. Carmichael lived in Bowie County, Texas, and sued Texarkana, Arkansas, in Arkansas federal court for a sewer discharge that damaged his property. His allegation was that Texarkana had built a sewer system with a single main line that ran to a point immediately opposite his homestead, near the border, and that this flow harmed him. Carmichael, 94 F. at 562. The court ordered Texarkana to stop the nuisance, citing a nearly unbroken line of authority across American courts, as well as English practice—the general or federal common law—rather than any distinct local law of Texas. Id. at 572.

Yet Boulder County did not pursue this sort of claim—a federal common-law claim in federal court. There is good reason for that. Climate-litigation groups originally asserted federal common-law claims in federal courts. The Supreme Court (in an opinion authored by Justice Ginsburg) in American Electric Power Co. v. Connecticut, 564 U.S. 410, 429 (2011), decisively dismissed that approach, holding that climate nuisance claims must be dismissed because the Clean Air Act displaced federal common law for interstate emissions.

Displacement and Preemption. This brings me to my second, and central, disagreement with Prof. Adler. He contends that the Clean Air Act’s displacement of federal common law opens the door for state-law regulation. “Federal common law may once have preempted state attempts to regulate interstate air pollution under state law, but federal common law has been displaced, and no longer serves that function.” Adler Br. at 3. The displacement of federal common law by the Clean Air Act thus quietly unpreempts certain state common-law claims. His key authority here is International Paper Co. v. Ouellette, 479 U.S. 481 (1987). In that case, Vermont landowners sued a New York paper mill under Vermont law for discharges into Lake Champlain originating in New York. The Court rejected the plaintiffs’ argument, holding that Vermont law could not reach discharges that occurred outside Vermont’s borders. As described above, interstate nuisance began as a body of federal common law. Ouellette holds that, although the Clean Water Act displaced that body of law, Congress did not thereby implicitly authorize states to apply their own distinct local law to out-of-state discharges. But Ouellette added that the Act’s savings clause “specifically preserved” the ability of courts to apply the law of the source state to those discharges. Id. at 497. The Court therefore remanded the case for proceedings under the proper state-law framework, as permitted by the Clean Water Act.

Prof. Adler asserts that Ouellette supports the conclusion that the Clean Air Act at least permits climate-change claims under the law of the source state, Adler Br. at 19–22, which he calls a “fundamental weakness of the substantive argument” raised by the defendants. See also Jonathan H. Adler, Displacement and Preemption of Climate Nuisance Claims, 17 J.L. Econ. & Pol’y 217, 255 (2022) (“Accordingly, state-law claims may proceed, so long as they rely upon the law of the source state[.]”). Prof. Adler is correct that the defendants contend that climate torts may not fit, even under Ouellette, but he omits their broader point that the Ouellette holding applies with equal force to the Clean Air Act: at most, you get the law of the source state or nothing, “no home cooking.” See Pet. Br. at 33–34.

I contend that petitioners are right to argue that climate tort claims do not resemble a traditional source-state action preserved by Ouellette. Suncor is not about a sewage discharge across a state line; it concerns global carbon emissions all mixed in the troposphere. Trying to regulate that with a hodgepodge of state tort laws would displace federal supremacy and risk the “chaotic confrontation between sovereign states” that Ouellette sought to avoid. 479 U.S. at 496–497.

Nevertheless, set that aside for the moment. Could Boulder County have alleged a case under the law of fifty states and 194 other countries for relief on a pro rata basis? If we accept Prof. Adler’s no-home-cooking rule, perhaps it could have.

Did it? No.

This is where Prof. Adler errs. To be sure, Boulder County’s brief opposing the petition hints that the choice of law has not yet been determined, as if eight years in no one had figured out which law was being invoked. That late pivot is not credible. For instance, page 1 of Boulder County’s brief to the Colorado Supreme Court states that “Plaintiffs seek damages under Colorado tort law,” and later adds that “[l]iability in this case is based on Colorado’s law of trespass, private and public nuisance, unjust enrichment, and civil conspiracy.” And the County asserted the same to the trial court: “Plaintiffs filed this case under Colorado’s common law…and its Consumer Protection Act….” In other words, Boulder County already made its choice.

The question before the Supreme Court is thus whether the state law under which Boulder County has pled its claims can apply to emissions elsewhere: Ouellette says that it cannot. That choice of law is preempted. There is no reason for the Court to delay a ruling. On Prof. Adler’s reasoning, then, the Court—at the very least—should reverse and remand in the same manner as it did in Ouellette.

Perhaps Prof. Adler agrees. But if so, why did he file his brief in support of the plaintiffs rather than the defendants, or in support of neither party?

[1] Full disclosure: my colleague Jared Kelson and I filed an amicus brief on behalf of 74 members of Congress in support of the Defendants in Suncor. Another colleague, Jen Hardy, filed a (very interesting) brief on behalf of Prof. Prakash in support of the Defendants as well. Prof. Eugene Volokh also co-authored an excellent brief on the free-speech implications of the case.

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Here are Professor Adler’s prior posts on Suncor and related climate litigation:

• Why State Common Law Nuisance Claims Against Fossil Fuel Companies Are Not Preempted, Oct. 27, 2021;
• Third Circuit Rejects Oil Company Efforts to Remove Climate Claims to Federal Court, Aug. 17, 2022;
• Oil Companies Fail to Convince the Eighth Circuit Climate Cases Should Be Removed to Federal Court (Updated), Mar. 25, 2023;
• Is Climate Change Going Back to the Supreme Court? (Minnesota Edition) [UPDATED], Dec. 11, 2023;
• D.C. Circuit Rejects Oil Company Attempt to Remove District’s Climate Suit to Federal Court, Dec. 19, 2023;
• William Barr Responds on American Petroleum Institute v. Minnesota, Dec. 26, 2023;
• Supreme Court Takes a Pass on Minnesota Climate Change Case, Jan. 8, 2024;
• Are State Law Climate Change Tort Suits Preempted by Federal Law?, May 3, 2024;
• Supreme Court Denies Certiorari in Climate Tort Suits, Jan. 13, 2025;
• Supreme Court Rejects Red State Attempt to Sue Blue States Over Climate Suits, Mar. 10, 2025;
• William Barr Discovers the Economics of Tort Law (and Misrepresents the Law Governing Interstate Pollution), Nov. 3, 2025;
• Placing Climate Tort Litigation in Context (Updated), Nov. 7, 2025;
• A Second Round with William Barr on Litigation Over Interstate Pollution, Dec. 2, 2025;
• Court Dismisses Trump Administration Effort to Block Michigan Climate Lawsuit, Feb. 4, 2026
• Climate Change Goes Back to the Supreme Court — Colorado Edition, Feb. 23, 2026.
• Previewing Suncor Energy v. Boulder County, Mar. 6, 2026.
• Amicus Brief in Suncor Energy v. County Commissioners of Boulder County, Aug. 3, 2026.
• Supreme Court Term to Start Hot, Aug. 6, 2026
• As Suncor Approaches, Justice Alito Recuses, Sept. 28, 2026.
• Justice Alito Says Recusal in Suncor Energy v. Boulder County a “Difficult Judgment Call”, Sept. 30, 2026

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