# Mayor & City Cncl. Of Balt. V. B.P. P.L.C.

> Court of Appeals of Maryland · March 24, 2026

URL: https://www.frixlaw.com/law-library/cases/11281058

## Case

- **Court:** Court of Appeals of Maryland
- **Decided:** March 24, 2026
- **Precedential status:** Published
- **Opinion:** Opinion
- **Judges:** Booth
- **Cited by:** 0 later opinions in the Frix Law Library

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## Opinion text

Mayor & City Council of Baltimore v. B.P. P.L.C., et al.; Anne Arundel County, Maryland
v. B.P. P.L.C., et al; City of Annapolis v. B.P. P.L.C., et al., No. 11, September Term, 2025,
Opinion by Booth, J.

FEDERAL DISPLACEMENT/PREEMPTION OF STATE LAW CLAIMS

The Supreme Court of Maryland considered three consolidated cases—one case filed in
the Circuit Court for Baltimore City and two cases filed in the Circuit Court for Anne
Arundel County. In these cases, the Mayor and Council of Baltimore City (“Baltimore”),
Anne Arundel County, and the City of Annapolis, (collectively, the “local governments”)
filed state common law tort claims against 26 multinational oil and gas companies to
recover damages caused by global greenhouse gas emissions. Specifically, the local
governments asserted five causes of action against the Defendants, all arising under
Maryland law: (1) public nuisance; (2) private nuisance; (3) trespass; (4) negligent failure
to warn; and (5) strict liability failure to warn.

The local governments argued that the Defendants, individually and collectively, are
responsible for extracting, processing, producing, promoting, and marketing fossil fuel
products, the normal and intended use of which has led to the emission of a substantial
percentage of the total volume of greenhouse gases released into the atmosphere for over
50 years. The local governments contend that the Defendants deceived consumers and the
public about the dangers associated with their fossil fuel products when they knew of a
direct link between their products and climate change threats, causing sea levels to rise, as
well as other physical and environmental impacts, resulting in inundation, destruction,
and/or other interference with the local governments’ property and citizenry.

The Circuit Court for Baltimore City and the Circuit Court for Anne Arundel County
granted the Defendants’ motions to dismiss. After an appeal to the Appellate Court of
Maryland, in which the cases were consolidated, this Court issued a bypass writ of
certiorari to determine whether Maryland local governments may bring the state common
law tort claims against the 26 companies to recover damages caused by global greenhouse
gas emissions.

The Supreme Court of Maryland affirmed the judgments of the lower courts dismissing the
complaints. The Court held that the local governments’ state law claims are displaced and
preempted by federal law. The Court determined that the local governments, through their
state law claims, are attempting to regulate air emissions. The Court explained that, for
over a century, the United States Supreme Court has held that cases involving regulations
of interstate pollution arise under federal law. Under the United States Supreme Court’s
jurisprudence, any state law claims are displaced by federal common law. Moreover, as
the United States Supreme Court held in American Electric Power Co., Inc. v. Connecticut,
564 U.S. 410 (2011), the Clean Air Act, 42 U.S.C. § 7401, et seq. (1970), displaces
applicable federal common law. Applying the preemption framework adopted by the
United States Supreme Court in International Paper Company v. Ouellette, 479 U.S. 481
(1987), the Supreme Court of Maryland held that the Clean Air Act does not authorize the
broad state law claims under its saving clause. Finally, the Supreme Court of Maryland
held that federal common law would not extend to apply to the local governments’ claims
that regulate international conduct. The United States Supreme Court has made it clear
that the political branches, not the Judiciary, have the responsibility and institutional
capacity to weigh foreign policy concerns.

The Supreme Court further held that, even if the local governments’ state law claims were
not displaced or preempted by federal law, the local governments failed to state legally
cognizable claims under state law for public nuisance, private nuisance, trespass, and
negligent and strict liability failure to warn.

PUBLIC NUISANCE

The Supreme Court held that the local governments failed to state a claim for public
nuisance under Maryland law. As this Court explained in Express Scripts, Inc. v. Anne
Arundel County, Maryland, ___ Md. _____ (filed March 23, 2026), Maryland has not
expanded the public nuisance doctrine beyond the traditional historical principles
embodied in the common law—namely, that a public nuisance action was not regarded as
a tort but was instead a public action by a government entity to pursue criminal
prosecutions or seek injunctive relief to abate harmful conduct. Additionally, this Court
has never recognized a government entity’s ability to recover damages for public nuisance.
Moreover, assuming without deciding that there is a public right to be free from adverse
effects of climate change, the Court stated that it nonetheless declines to expand
Maryland’s common law of public nuisance to govern the conduct alleged in the local
governments’ complaints given the extensive federal statutory and regulatory framework
that governs the highly complex conduct of regulating air emissions.

PRIVATE NUISANCE

The Supreme Court held that the local governments failed to state a claim for private
nuisance because that tort requires that the plaintiff establish an injury to property that is
different in kind from that suffered by the public generally. Here, the injuries alleged by
the local governments are not unique or different from any injuries suffered by the public
generally.

TRESPASS

The Court held that the local governments’ trespass claim exceeds the bounds of the tort
established in this Court’s case law, which holds that when an adjacent property is invaded
by an inanimate or intangible object, the defendant must have some connection or control
over that object for a trespass action to lie. The Court agreed with the Circuit Court for
Baltimore City that the link between the Defendants’ activities and the harms alleged by
the local governments, which are caused by human activities around the world, are far too
attenuated to constitute the Defendants’ connection or control over the rainfall and storms
that invaded the local governments’ property.

STRICT LIABILITY/NEGLIGENCE ARISING FROM FAILURE TO WARN

The Court held that the local governments failed to state claims for strict liability and
negligent failure to warn. The Court determined that the duty the local governments seek
to impose is a duty to warn the entire human race of the effects of climate change. The
Court stated that finding such a duty would stretch Maryland tort law beyond manageable
bounds.
Circuit Court for Baltimore City
Case No.: 24-C-18-004219
IN THE SUPREME COURT
Circuit Court for Anne Arundel County
Case No.: C-02-CV-21-000250
OF MARYLAND

Circuit Court for Anne Arundel County
Case No.: C-02-CV-21-000565 No. 11
September Term, 2025
Argued: October 6, 2025

MAYOR & CITY COUNCIL OF BALTIMORE
v.
B.P. P.L.C., et al.

ANNE ARUNDEL COUNTY, MARYLAND
v.
B.P. P.L.C., et al.

CITY OF ANNAPOLIS
v.
B.P. P.L.C., et al.

Fader, C.J.,
Watts,
Booth,
Gould,
Eaves,
Killough,
Battaglia, Lynne A.
(Senior Justice, Specially Assigned)

JJ.

Opinion by Booth, J.
Fader, C.J., concurs.
Gould, J., concurs.
Watts, J., concurs and dissents.
Pursuant to the Maryland Uniform Electronic Legal Killough, J., concurs and dissents.
Materials Act (§§ 10-1601 et seq. of the State
Government Article) this document is authentic.

2026.03.24 Filed: March 24, 2026
13:47:24 -04'00'
Gregory Hilton, Clerk
The question presented in this case is whether Maryland local governments may

bring state common law tort claims against 26 multinational oil and gas companies to

recover damages caused by global greenhouse gas emissions. We hold that they may not.

For the reasons set forth more fully herein, we determine that state common law has

never applied to the conduct alleged by the local governments. We determine that the local

governments, through their various state law claims, are seeking to regulate air emissions

beyond their jurisdictional boundaries. For over a century, the United States Supreme

Court has held that cases involving regulation of interstate pollution arise under federal

law. Under the United States Supreme Court’s jurisprudence, we conclude that any state

law claims are displaced by federal common law. Moreover, as the United States Supreme

Court held in American Electric Power Co., Inc. v. Connecticut, 564 U.S. 410 (2011), the

Clean Air Act, 42 U.S.C. § 7401, et seq. (1970), displaces applicable federal common law.

Applying the preemption framework adopted by the Supreme Court in International Paper

Company v. Ouellette, 479 U.S. 481 (1987), we hold that that the Clean Air Act does not

authorize the broad state law claims under its saving clause. Additionally, to the extent

that the local governments seek recovery for harms caused by foreign emissions, foreign

policy concerns would foreclose a federal common law action targeting emissions

emanating from beyond our borders.

Finally, we hold that, even if the local governments’ state law claims were not

displaced or preempted by federal law, they fail to state claims under Maryland law for

public and private nuisance, strict liability and negligent failure to warn, and trespass. We

discuss the legal deficiencies pertaining to each of these state law claims below.
This appeal comprises three consolidated cases—one filed in the Circuit Court for

Baltimore City and two filed in the Circuit Court for Anne Arundel County. These cases

took an extended detour through the federal courts arising from the oil and gas companies’

unsuccessful attempts at removal. We briefly recount the circuitous route that brought

these cases to this Court.

I

Procedural History

A. Baltimore City Case

1. Complaint

In July 2018, the Mayor and City Council of Baltimore (“Baltimore”) filed suit

against 26 major oil and gas companies (“the Defendants”) 1 in the Circuit Court for
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Baltimore City. Baltimore asserts that the Defendants substantially contributed to

greenhouse gas pollution, global warming, and climate change by extracting, producing,

promoting, refining, marketing, distributing, and selling fossil fuel products (i.e., coal, oil,

and natural gas). Baltimore contends that the Defendants deceived consumers and the

1
The Defendants consist of BP entities (BP P.L.C.; BP America, Inc.; and BP
Products North America Inc.); Crown Central entities (Crown Central Petroleum
Corporation; Crown Central LLC; and Crown Central New Holdings LLC); Chevron
entities (Chevron Corp. and Chevron U.S.A. Inc.); Exxon Mobil entities (Exxon Mobil
Corp. and ExxonMobil Oil Corporation); Shell entities (Royal Dutch Shell PLC and Shell
Oil Company); Citgo Petroleum Corp.; ConocoPhillips entities (ConocoPhillips;
ConocoPhillips Company; Louisiana Land & Exploration Co.; Phillips 66; and Phillips 66
Company); Marathon entities (Marathon Oil Company; Marathon Oil Corporation;
Marathon Petroleum Corporation; and Speedway LLC); Hess Corp.; and CONSOL entities
(CNX Resources Corporation; CONSOL Energy Inc.; and CONSOL Marine Terminals
LLC).
2
public about the dangers associated with their fossil fuel products when they knew for

nearly 50 years of a direct link between their products and climate change threats. With

that knowledge, Baltimore alleges, the Defendants (1) employed a “coordinated, multi-

front effort to conceal and deny their own knowledge of those threats”; (2) discredited

“publicly available scientific evidence”; and (3) created persistent doubt within the public

sphere about the “reality and consequences of the impacts of their fossil fuel pollution.”

According to Baltimore, the “Defendants, individually and collectively, are

responsible for extracting, processing, producing, promoting, and marketing fossil fuel

products, the normal and intended use of which has led to the emission of a substantial

percentage of the total volume of greenhouse gases released into the atmosphere” for over

50 years. The Defendants’ conduct that caused these emissions, Baltimore asserts,

includes, but is not limited to, their: (1) “extraction, refining, and/or formulation of fossil

fuel products;” (2) “introduction of fossil fuel products into the stream of commerce;” (3)

“wrongful promotion of their fossil fuel products and concealment of known hazards

associated with use of those products;” and (4) “failure to pursue less hazardous

alternatives available to them[.]” The above-described conduct is allegedly a “substantial

factor in causing the increase in global mean temperature and consequent increase in global

mean sea surface height and disruption to the hydrologic cycle, including, but not limited

to, more frequent and extreme droughts, more frequent and extreme temperatures, and the

associated consequences of those physical and environmental changes since 1965.”

The Defendants’ conduct is alleged to have (1) “actually and proximately caused

the sea levels to rise,” (2) “increased coastal erosion,” (3) “increased the destructive

3
impacts of storm surges,” (4) “exacerbated the onshore impact of regular tidal ebb and

flow,” (5) “disrupted the hydrologic cycle,” (6) “caused increased frequency and severity

of drought,” “extreme precipitation events,” and “heat waves,” and (7) “caused consequent

social and economic injuries associated with the aforementioned physical and

environmental impacts . . . resulting in inundation, destruction, and/or other interference

with” Baltimore’s “property and citizenry.” These environmental events have purportedly

caused, among other things, infrastructure damage during floods, automobile accidents and

power outages when winter storms hit, and public-health illnesses amid heat waves.

At bottom, Baltimore attempts to shift the burden of its climate change costs onto

the Defendants. Specifically, Baltimore “seeks to ensure that the parties who have profited

from externalizing the responsibility for sea level rise, extreme precipitation events,

heatwaves, other results of the changing hydrologic regime caused by increasing

temperatures, and associated consequences of those physical and environmental changes,

bear the costs of those impacts on” Baltimore, rather than the City, “local taxpayers,

residents, or broader segments of the public.” Baltimore, however, alleges that it “does not

seek to impose liability on the Defendants for their direct emissions of greenhouse gases

and does not seek to restrain the Defendants from engaging in their business operations.”

Baltimore asserts five causes of action against the Defendants, all arising under

Maryland law: (1) public nuisance; (2) private nuisance; (3) strict liability for failure to

4
warn; (4) negligent failure to warn; and (5) trespass. 2 To remedy its injuries, Baltimore
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seeks compensatory and punitive damages, disgorgement of profits, and equitable relief,

including the abatement of the alleged nuisances and an injunction against future nuisances.

2. Removal Proceedings

After Baltimore’s suit was filed in state court in July 2018, the Defendants timely

removed Baltimore’s complaint to the United States District Court for the District of

Maryland. The Defendants asserted eight different grounds for removal under statutory

grants of federal jurisdiction and various legal theories. Mayor & City Council of Balt. v.

BP P.L.C., 388 F. Supp. 3d 538 (D. Md. 2019). In response, Baltimore filed a motion to

remand its complaint to the Circuit Court for Baltimore City. Id. at 550. The district court

granted Baltimore’s motion to remand in June 2019, rejecting each of the Defendants’ eight

grounds for removal. Id. at 574. The Defendants appealed the district court’s remand order

to the United States Court of Appeals for the Fourth Circuit. Mayor & City Council of

Balt. v. BP P.L.C., 952 F.3d 452 (4th Cir. 2020). That court reasoned that it could analyze

the propriety of removal only under the federal officer removal statute and that it lacked

appellate jurisdiction over the remaining seven grounds for removal. Id. at 461. The Fourth

Circuit ultimately held that federal officer removal was improper, affirming the district

court’s remand order on that sole ground. Id. at 461–70.

2
In the complaint, Baltimore also alleged design-defect claims and violations of the
Maryland Consumer Protection Act, Md. Code (2025 Repl. Vol.), Com. Law §§ 13-101–
501. Baltimore has not appealed the dismissal of those counts. Accordingly, those claims
are not before us.
5
The Defendants appealed to the United States Supreme Court, which vacated the

Fourth Circuit’s opinion and remanded the case for further proceedings. BP P.L.C. v.

Mayor & City Council of Balt., 593 U.S. 230 (2021). The Supreme Court held that the

Fourth Circuit was not divested of appellate jurisdiction over the Defendants’ other theories

of removal and remanded the case to that court for it to consider all the bases for removal

included in the district court’s remand order. Id. On remand, the Fourth Circuit evaluated

the remaining theories of removal proffered by the Defendants and affirmed the district

court’s order granting Baltimore’s motion to remand. Mayor & City Council of Balt. v. BP

P.L.C., 31 F.4th 178 (4th Cir. 2022). 3 The Supreme Court denied the Defendants’ petition
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for writ of certiorari, BP P.L.C. v. Mayor & City Council of Balt., 143 S. Ct. 1795 (2023),

and the case was remanded to the Circuit Court for Baltimore City.

3. Circuit Court’s Ruling on Defendants’ Motion to Dismiss

When the case returned to state court, the Defendants filed a motion to dismiss the

complaint for failure to state a claim upon which relief could be granted. In their motion,

the Defendants asserted that the complaint must be dismissed because Baltimore’s claims

are preempted by federal common law and the Clean Air Act. Assuming the individual

claims are not preempted by federal law, the Defendants contended that each of the claims

3
The removal grounds asserted by the Defendants were as follows: (1) federal
common law; (2) substantial issues of federal law, as well as foreign affairs, under Grable
& Sons Metal Products, Inc. v. Darue Engineering & Manufacturing, 545 U.S. 308 (2005);
(3) complete preemption under the Clean Air Act, 42 U.S.C. §§ 7401–7671q; (4) federal
enclaves; (5) the Outer Continental Shelf Lands Act, 43 U.S.C. § 1349(b)(1); (6) the
bankruptcy removal statute, 28 U.S.C. § 1452(a); (7) the admiralty jurisdiction statute, 28
U.S.C. § 1333(1); and (8) the federal officer removal statute, 28 U.S.C. § 1442(a)(1).
Mayor & City Council of Balt. v. BP P.L.C., 31 F.4th 178, 196 (4th Cir. 2022).
6
alleged by Baltimore are legally deficient under state law. After Baltimore filed a response

and following a hearing, the circuit court issued a memorandum opinion and order in July

2024 granting the Defendants’ motion to dismiss.

In its memorandum opinion and order, the court ruled that, regardless of how

Baltimore characterized its complaint, “the Constitution’s federal structure does not allow

the application of state law claims like those presented by Baltimore.” The court explained

that “[g]lobal pollution-based complaints were never intended by Congress to be handled

by individual states.” The court also determined that the Clean Air Act “speaks directly to

the domestic emissions issues in this case[]” and thus preempts Baltimore’s claims. The

court also ruled that “[f]ederal common law is still required to apply to extraterritorial

aspects of claims challenging undifferentiated global emissions.”

In addition to ruling that the claims were preempted by federal law, the circuit court

also concluded that Baltimore failed to state claims under Maryland law. The court

dismissed Baltimore’s nuisance claims because it concluded that Maryland’s common law

of public nuisance applied only to “cases involving a defendant’s use of land[,]” and did

not apply to “product liability cases.” The court dismissed the failure-to-warn claims

because the court determined that they were based on a duty to “warn the world[.]”

Regarding trespass, the court found the theories of harm too “attenuated to constitute the

control necessary to establish liability” under existing law and declined to “extend trespass

liability beyond where the Maryland Supreme Court has previously allowed.” 4 3F

4
As previously noted, see supra n.2, the court also dismissed Baltimore’s design
defect and MPCA claims, and Baltimore did not appeal the dismissal of those claims.
7
B. Anne Arundel County and Annapolis Cases

1. The Complaint

In February 2021, Anne Arundel County (“the County”) and the City of Annapolis

(“Annapolis”) each filed nearly identical suits in the Circuit Court for Anne Arundel

County against a similar list of defendants as those named in the Baltimore litigation, with

minor exceptions. The County and Annapolis both amended their complaints in June 2024.

Although the allegations set forth in the County’s and Annapolis’s complaints are

substantively similar to Baltimore’s (a point conceded by the local governments in their

brief), we briefly touch upon the allegations set forth in the County’s and Annapolis’s

nearly identical operative complaints, which total approximately 350 pages.

The County and Annapolis assert that the “Defendants are directly responsible for

the substantial increase in all CO2 emissions” for the past 50 years. The County and

Annapolis allege that the “Defendants’ individual and collective conduct, including, but

not limited to, their”: (1) “introduction of fossil fuel products into the stream of commerce

while knowing but failing to warn of the threats posed to the world’s climate;” (2)

“wrongful promotion of their fossil fuel products and concealment of known hazards

associated with the use of those products;” (3) “public deception campaigns designed to

obscure the connection between their products and global warming and the environmental,

physical, social, and economic consequences flowing from it;” and (4) “failure to pursue

less hazardous alternatives[,]” which actually and proximately caused the County’s and

Annapolis’s injuries. “In other words,” according to the County and Annapolis, the

“Defendants’ concealment and misrepresentation of their products’ known dangers—and

8
simultaneous promotion of their products for uses Defendants knew were harmful—drove

consumption, and thus greenhouse gas pollution, and thus the climate crisis.”

As examples of the tortious conduct that allegedly caused the injuries, the County

and Annapolis specifically identify the Defendants’ internal corporate policies and

communications, their membership and financial contributions to organizations that

engaged with the public and government on climate change, and their external

communication and advertising on the matter.

The County and Annapolis assert the same state law causes of action as those alleged

by Baltimore and seek the same relief—compensatory damages, disgorgement of profits,

and equitable relief, including the abatement of the alleged nuisances and an injunction

against future nuisances.

2. Removal Proceedings

Following the same playbook as the Baltimore litigation, the Defendants removed

the case to federal court. City of Annapolis, Maryland v. BP P.L.C., No. CV SAG-21-

00772, 2022 WL 458226 (D. Md. Sept. 29, 2022). The County and Annapolis filed

motions to remand to state court, which the district court granted. After the Defendants

appealed, the Fourth Circuit affirmed the district court’s judgment, concluding that there

was no valid basis for removal. Anne Arundel County, Maryland v. BP P.L.C., 94 F.4th

343 (4th Cir. 2024).

3. Circuit Court’s Proceedings on Motion to Dismiss

Upon the case’s return to the circuit court, the Defendants filed a motion to dismiss,

and the County and Annapolis filed responses in opposition. The Circuit Court for Anne

9
Arundel County entered an order in January 2025 dismissing the cases “on the grounds of

preemption for essentially the same reasons” as the dismissal of Baltimore’s case.

C. Appellate Proceedings

Baltimore, the County, and Annapolis each appealed to the Appellate Court of

Maryland. The Appellate Court consolidated the cases after the Defendants jointly moved

to consolidate the appeals. The Defendants filed an unopposed bypass petition for writ of

certiorari with this Court, and the local governments collectively filed a cross-petition for

writ of certiorari. We granted certiorari and ordered that the case be transferred from the

Appellate Court to this Court.

II

Questions Presented and Parties’ Contentions

The questions before us can be distilled as follows: (1) whether the state law claims

asserted by the local governments are displaced or preempted by federal law; and, if not,

(2) whether the claims are legally cognizable under state law.

The local governments assert that the circuit courts erred in dismissing their state

law claims. According to the local governments, the courts (1) “fundamentally

misconstrued” their cases, (2) erred in concluding that the claims involve the regulation of

emissions, (3) “recharacterized” their claims as being “entirely about addressing the

injuries of climate change,” and (4) did not accept the local governments’ description of

the goals of their complaint. Had the circuit courts properly considered the claims asserted,

the local governments contend, the courts would not have found that the claims were

preempted by the structure of the United States Constitution, the Clean Air Act, and “a

10
defunct body of federal common law that the” Clean Air Act displaced. The local

governments assert that the courts erred in failing to consider the claims, and reasonable

interferences to be drawn therefrom, in the light most favorable to the local governments.

Viewing the allegations in the complaint through the correct lens, the local governments

argue that their claims do not regulate air emissions and urge us to follow the decisions of

the Supreme Courts of Hawaii and Colorado, which have determined that similar claims

relate only to a defendant’s “use of deception to promote the consumption of fossil fuel

products,” and do not concern emissions standards. See City & County of Honolulu v.

Sunoco LP, 537 P.3d 1173 (Haw. 2023), cert. denied, 145 S. Ct. 1111 (2025) (No. 23-947)

(“Honolulu”); County Comm’rs of Boulder County v. Suncor Energy USA, Inc., No.

24SA206, 2025 WL 1363355 (Co. 2025), cert. granted, ___ S. Ct. ___, 2026 WL 490537

(2026) (“Boulder”). The local governments assert that remedying the deceptive and

commercial conduct as alleged in their complaints is “within the core of” their “state police

powers.”

The local governments also contend that they have pled actionable claims under

Maryland law, and that the Circuit Court for Baltimore City erred in dismissing Baltimore’s

claims for private and public nuisance, trespass, and failure to warn.

The Defendants argue that the circuit courts did not mischaracterize the local

governments’ claims. They assert that we should follow the Court of Appeals for the

Second Circuit, which considered similar claims and rejected the contention that they

simply relate to deceptive marketing and promotion and do not involve air emissions. See

City of New York v. Chevron Corp., 993 F.3d 81, 91 (2d. Cir. 2021). According to the

11
Defendants, when the local governments’ claims are viewed for what they are—attempts

to regulate global conduct through claims for damages and injunctive relief related to

injuries arising from climate change—the claims are preempted by the structure of the

United States Constitution and federal law.

The Defendants also argue that the Circuit Court for Baltimore City did not err in

determining that each of the state common law claims failed to satisfy key elements

necessary to establish the claims under state law.

III

Standard of Review

The questions before us are matters of law that we review de novo. Plank v.

Cherneski, 469 Md. 548, 569 (2020). They arise from the circuit courts’ dismissal of the

complaints on the ground that they fail to state a claim upon which relief can be granted.

We review a circuit court’s grant of a motion to dismiss without deference to determine

whether it was legally correct. Wheeling v. Selene Finance LP, 473 Md. 356, 374 (2021).

We assume the truth of all relevant and material facts that are well pleaded, as well as the

inferences that can be reasonably drawn from those pleadings, in the light most favorable

to the nonmoving party. Id. “A motion to dismiss on this ground may only be granted

when the allegations presented do not state a cause of action.” Id. “In the interest of

judicial efficiency, we may affirm the judgment of a trial court to grant a motion to dismiss

on a different ground than that relied upon by the trial court, as long as the alternative

ground is before the Court properly on the record.” Forster v. State, Off. of Pub. Def., 426

Md. 565, 580–81 (2012); see also City of Frederick v. Pickett, 392 Md. 411, 424 (2006)

12
(stating that an appellate court can affirm a dismissal on any ground adequately shown by

the record, whether or not relied upon by the trial court).

IV

Federal Law Background

To address the Defendants’ arguments that the local governments’ claims are

displaced or preempted by federal law, it is instructive to discuss the United States Supreme

Court’s and lower federal courts’ cases that have addressed interstate pollution. Before we

turn to the cases, however, we discuss two landmark environmental statutes that Congress

enacted in the 1970s to address pollution—the Clean Water Act and the Clean Air Act. We

describe this statutory framework because these laws play prominent roles in the discussion

of the applicable case law, as well as in our preemption analysis.

A. Federal Statutes

1. The Clean Water Act

Although Congress enacted the Federal Water Pollution Control Act in 1948, it was

significantly reorganized, and Congress expanded the law in 1972 to become what is now

commonly referred to as the “Clean Water Act.” 33 U.S.C. § 1251 et seq. (1972). Congress

enacted the Act “to restore and maintain the chemical, physical, and biological integrity of

the Nation’s waters.” Id. § 1251(a). Among its core provisions, the Clean Water Act

prohibits discharging pollutants into waters of the United States, except as authorized by a

permit issued under the National Pollution Discharge Elimination System (“NPDES”). See

id. §§ 1251(a)(1), 1311(a), 1342(a)(1). An NPDES permit places limits—called “effluent

limitations”—on the type and quantity of pollutants that can be released into the Nation’s

13
waters. The Act authorizes the U.S. Environmental Protection Agency (“EPA”) to issue

and enforce these permits, id. §§ 1319, 1342(a)(1), as well as to delegate its NPDES

permitting authority to a state, id. §§ 1342(b). 5 We address additional provisions of the
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Act in the context of our discussion of case law below.

2. The Clean Air Act

The Clean Air Act is a comprehensive federal law that regulates air emissions from

stationary and mobile sources. 6 42 U.S.C. § 7401 et seq. (1970). “It is an intricate
5F

regulatory regime intended to ‘protect and enhance the quality of the [n]ation’s air

resources so as to promote the public health and welfare and the productive capacity of its

population.’” N.Y. Pub. Inst. Rsch. Grp. v. Whitman, 321 F.3d 316, 319–20 (2d Cir. 2003)

(quoting 42 U.S.C. § 7401(b)(1)). In Massachusetts v. EPA, the Supreme Court held that

the Act authorizes federal regulation of emissions of carbon dioxide and other greenhouse

gases. 549 U.S. 497 (2007).

“The Clean Air Act regulates air quality through a federal-state collaboration.”

Ohio v. EPA, 603 U.S. 279, 283 (2024) (citation modified). In a nutshell, the EPA is

5
The Clean Water Act is vast and extraordinarily complex. We touch upon only
key aspects of the Act for the limited purpose of providing context for the Supreme Court’s
and lower federal courts’ displacement and preemption analysis of nuisance claims related
to interstate pollution brought under federal and state common law.
6
The Clean Air Act regulates air pollution from stationary sources, 42 U.S.C.
§§ 7401–7431, and establishes emission standards for moving sources, including motor
vehicles, id. §§ 7521–7554, aircrafts, id. §§ 7571–7574, clean fuel vehicles, id. §§ 7581–
7574; acid deposition control, id. §§ 7651–7651o; and stratospheric ozone protection, id.
at §§ 7671–7671q. It also provides a means for citizen suits, id. § 7604, and outlines a
permitting process for emission standards, id. §§ 7661–7661f.
14
required to set “national primary or secondary ambient air quality standards” (or

“NAAQS”) for common air pollutants, 7 which “represent[] ‘the maximum airborne
6F

concentration that the public health can tolerate.’” West Virginia v. EPA, 597 U.S. 697,

707 (2022) (quoting Whitman v. Amc. Trucking Ass’ns, Inc., 531 U.S. 457, 465 (2001));

see also 40 C.F.R. pt. 50 (2013). “States bear ‘primary responsibility’ for deciding how a

NAAQS should be attained.” Oklahoma v. EPA, 605 U.S. 609, 615 (2025) (quoting 42

U.S.C. § 7401(a)(3)). This is accomplished through “state implementation plans” or state

proposals that ensure compliance with the NAAQS for each criteria pollutant. See 42

U.S.C. § 7410. Through its state implementation plan, each state is required to “‘provid[e]

for [the] implementation, maintenance, and enforcement’ of a NAAQS within their

jurisdictions.” Oklahoma, 605 U.S. at 615 (quoting 42 U.S.C. § 7410(a)(1)). The Clean

Air Act authorizes the states to decide how to measure ambient air quality, 42 U.S.C. §

7410(a)(2)(B), and pick “emission limitations and other control measures[,]” id. §

7410(a)(2)(A).

“While states are responsible for promulgating” state implementation plans, “they

must do so consistently with extensive EPA regulations governing preparation, adoption

by the state, and submission to the EPA, 40 C.F.R. § 51, and all [state plans] must be

7
The Clean Air Act broadly defines “air pollutant” to include “any air pollution
agent or combination of such agents, including any physical, chemical . . . substance or
matter which is emitted into or otherwise enters the ambient air.” 42 U.S.C. § 7602(g). The
EPA has established national primary or secondary ambient air quality standards
(“NAAQS”) for six pollutants—carbon monoxide, lead, nitrogen dioxide, ozone,
particulate matter, and sulfur dioxide. See Env’t Prot. Agency, Criteria Air Pollutants (Jan.
23, 2026), https://perma.cc/37CF-4DR8; see also 40 C.F.R. pt. 50 (2013).
15
submitted to the EPA for approval before they become final.” North Carolina, ex rel.

Cooper v. Tenn. Valley Auth., 615 F.3d 291, 299 (4th Cir. 2010) (citing 42 U.S.C.

§ 7410(a)(1), (k)(2) & (3)). 8 7F Once a state implementation plan is approved, “its

requirements become federal law and are fully enforceable in federal court.” Id. (citing

§ 7604(a)) (additional citations omitted).

Although states are accorded flexibility in determining how their state

implementation plans are structured, the plans must “include enforceable emission

limitations and other control measures, means, or techniques” to ensure that each state

meets NAAQS. 42 U.S.C. § 7410(a)(2)(A). 9 “States are also tasked with enforcing the
8F

limitations they adopt in their [plans].” Tenn. Valley Auth., 615 F.3d at 299. “They must

regulate ‘the modification and construction of any stationary source within the areas

covered by the [state implementation plan],’ 42 U.S.C. § 7410(a)(2)(C), and must

8
If the EPA does not approve a state implementation plan, then the EPA must issue
a “Federal implementation plan” for the noncompliant state within two years. 42 U.S.C.
§ 7410(c)(1). A state can avoid this outcome only if it corrects the deficiency and gains
EPA approval for its revised state implementation plan before the EPA promulgates the
federal plan. Id. § 7410(k)(3), (c)(1).
9
A state must designate every area within its borders as “attainment,”
“nonattainment,” or “unclassifiable” with respect to each NAAQS, 42 U.S.C. § 7407(d),
and the state implementation plan must include permitting programs for stationary sources
that vary according to the classification of the area where the source is or is proposed to be
located, id. § 7410(a)(2)(C), (I). Areas that comply with the NAAQS are “attainment
areas” and areas that do not comply are “nonattainment areas.” See generally id. § 7410.
To prevent attainment areas from getting dirtier, the Prevention of Significant Deterioration
program requires a new or modified “major emitting facility” of “any air pollutant” in those
areas to obtain permits and install the “best available control technology” for their
emissions. Id. § 7475(a)(4). The Clean Air Act defines a “major emitting facility” as any
stationary source with the potential to emit 250 tons per year of “any air pollutant” (or 100
tons per year for certain types of sources). Id. § 7479(1).
16
implement a permit program that limits the amounts and types of emissions that each

permit holder is allowed to discharge, 42 U.S.C. §§ 7661a(d)(1), 7661c(a).” Id. “Sources

are prohibited from operating without such a permit,” 42 U.S.C. § 7661a(a), “and each

permit is intended to be a source-specific bible for Clean Air Act compliance containing in

a single, comprehensive set of documents, all [Clean Air Act] requirements relevant to the

particular polluting source.” Tenn. Valley Auth., 615 F.3d at 299–300 (citation modified).

Notably, “states must design these plans with their neighbors in mind.” Ohio, 603

U.S. at 283. “Because air currents can carry pollution across state borders, emissions in

upwind States sometime affect air quality in downwind States.” Id. at 283–84. “To address

that externality problem,” the Act contains a “Good Neighbor Provision,” which provides

that state plans “must prohibit emissions ‘in amounts which will . . . contribute significantly

to nonattainment in, or interfere with maintenance by, any other State’ of the relevant air-

quality standard.” Id. at 284 (quoting 42 U.S.C. § 7410(a)(2)(D)(i)(I)).

Additionally, before new construction or modification of a source of emission may

begin, a state implementation plan must provide “written notice to all nearby States the air

pollution levels of which may be affected by such source at least sixty days prior to the

date on which commencement of construction is to be permitted[.]” 42 U.S.C. §

7426(a)(1)(B).

“In addition to this framework, there are a number of checks built into the system

to prevent abuses and to address concerns about emissions.” Tenn. Valley Auth., 615 F.3d.

at 300. As noted above, the EPA retains the ultimate authority over NAAQS to determine

what level of emissions are acceptable and has the responsibility to modify those levels as

17
necessary. 42 U.S.C. § 7409(b)(1), (2). The Clean Air Act provides a process for what is

commonly referred to as a “Section 126 petition,” which gives a state the authority to ask

the EPA to find that specific sources of air pollution in other states are significantly

contributing to non-attainment or interfering with maintenance of federal air quality

standards in the petitioning state. Id. § 7426(b). We touch upon additional provisions of

the Act as relevant to our discussion of the case law.

B. What is Federal Common Law?

Prior to Congress’s enactment of the extensive environmental legislation

comprising the Clean Water Act and Clean Air Act, disputes concerning interstate water

and air pollution were governed by federal common law. Before we discuss the cases

applying federal common law in the interstate pollution context, we first provide an

overview of what federal common law is, including its rationale and the limited number of

situations in which it arises.

The Supreme Court famously pronounced in Erie Railroad Company v. Tompkins

that “[t]here is no federal general common law.” 304 U.S. 64, 78 (1938). Although the

Court declared that there is no general federal common law, it has recognized that there

are some limited areas in which federal common law, or a federal rule of decision is

“necessary to protect uniquely federal interests.” Tex. Indus., Inc. v. Radcliff Materials,

Inc., 451 U.S. 630, 640 (1981) (citation modified); see also Rodriguez v. Fed. Deposit Ins.

Corp., 589 U.S. 132, 136 (2020) (explaining that federal common law still exists in certain

contexts and “often plays an important role”).

18
Federal common law exists in only a “few and restricted” enclaves, Wheeldin v.

Wheeler, 373 U.S. 647, 651 (1963), where a federal court is “compelled to consider federal

questions ‘which cannot be answered from federal statutes alone,’” City of Milwaukee v.

Illinois and Michigan (“Milwaukee II”), 451 U.S. 304, 314 (1981) (citation modified).

Once Congress speaks directly to those questions, “the need for such an unusual exercise

of lawmaking by federal courts disappears.” Id. The Court of Appeals for the Second

Circuit has aptly described federal common law as the functional equivalent of “legal duct

tape”—a “‘necessary expedient’ that permits federal courts to address issues of national

concern until Congress provides a more permanent solution.” City of New York, 993 F.3d

at 90 (quoting Milwaukee II, 451 U.S. at 314).

“Despite its utility,” our constitutional architecture “restricts federal common law

to a ‘modest role.’” Id. (quoting Rodriguez, 589 U.S. at 136). There are good reasons for

the limitation. Where federal common law exists, it “pre-empt[s] and replace[s]” state law,

Boyle v. United Techs. Corp., 487 U.S. 500, 504 (1988); see also Milwaukee II, 451 U.S.

at 313 n.7 (explaining that “if federal common law exists, it is because state law cannot be

used”). “It thus threatens a potent mix of judicial lawmaking and encroachment on our

federalist structure.” City of New York, 993 F.3d at 90.

The few and restricted categories in which federal common law exists “fall into

essentially two categories: those in which a federal rule of decision is necessary to protect

uniquely federal interests, and those in which Congress has given the courts the power to

develop substantive law[.]” Tex. Indus., Inc., 451 U.S. at 640 (citation modified); see also

Am. Elec. Power Co., v. Connecticut (“AEP”), 564 U.S. 410, 421 (2011) (acknowledging

19
that federal common law “addresses subjects within national legislative power where

Congress has so directed or where the basic scheme of the Constitution so demands”

(citation modified)).

The Supreme Court has stated that “absent some congressional authorization to

formulate substantive rules of decision, federal common law exists only in such narrow

areas as those concerned with” (1) “the rights and obligations of the United States”; (2)

“interstate and international disputes implicating the conflicting rights of States or our

relations with foreign nations”; and (3) “admiralty cases.” Tex. Indus., Inc., 451 U.S. at

641 (footnotes omitted). 10 “In these instances, our federal system does not permit the
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controversy to be resolved under state law, either because the authority and duties of the

United States as sovereign are intimately involved or because the interstate or international

nature of the controversy makes it inappropriate for state law to control.” Id.

“As these narrow categories suggest, the mere existence of a federal interest does

not intrinsically call for a corresponding federal rule.” City of New York, 993 F.3d at 90

(citing Empire Healthchoice Assurance, Inc. v. McVeigh, 547 U.S. 677, 692 (2006)).

10
In Atherton v. Federal Deposit Insurance Corporation, 519 U.S. 213 (1997), the
Court declined to fashion a general federal common law standard of care for officers and
directors of federally insured institutions. As part of its discussion, the Court cited cases
in which it had created federal common law. Id. at 225–26; see, e.g., Hinderlider v. La
Plata River & Cherry Creek Ditch Co., 304 U.S. 92, 110 (1938) (concerning controversy
between two states over administration of water rights); Boyle v. United Techs. Corp., 487
U.S. 500, 504 (1988) (concerning liability of independent contractors working for the
federal government); U.S. v. Standard Oil Co. of Cal., 332 U.S. 301, 305 (1947) (pertaining
to question of federal government’s entitlement to recover losses for tort against
servicemember); Howard v. Lyons, 360 U.S. 593, 597 (1959) (concerning liability of
federal officers in the course of official duty); Banco Nacional de Cuba v. Sabbatino, 376
U.S. 398, 425 (1964) (arising in context of relationships with other countries).
20
“There also must be a conflict between that federal interest and the operation of state law.”

Id. (footnote omitted) (citing Empire Healthchoice Assurance, Inc., 547 U.S. at 692); see

also O’Melveny & Myers v. FDIC, 512 U.S. 79, 87 (1994) (stating that conflict between

federal interest and use of state law is required to be a “precondition for recognition of a

federal rule of decision”); Boyle, 487 U.S. at 507. That said, the conflict between state law

and federal interests does not need to be “intractably severe before federal common law

may spring into action.” City of New York, 993 F.2d at 90. Indeed, as the Supreme Court

has explained, the necessary conflict “need not be as sharp as that which must exist for

ordinary pre-emption when Congress legislates in a field which the [s]tates have

traditionally occupied.” Boyle, 487 U.S. at 507 (internal citation omitted). “But conflict

there must be.” Id. at 508.

C. Cases Applying Federal Law to Claims Arising from Interstate Pollution

Interstate water and air pollution are areas that the Supreme Court and lower federal

courts have determined are governed by federal common law and, therefore, leave no place

for the application of state law. As the Court of Appeals for the Second Circuit observed,

“[f]or over a century, a mostly unbroken string of cases has applied federal law to disputes

involving interstate air or water pollution.” City of New York v. Chevron Corp., 993 F.3d

81, 91 (2d. Cir. 2021) (citing AEP, 564 U.S. 421; Int’l Paper Co. v. Ouellette, 479 U.S.

481, 487–89 (1987); Milwaukee II, 451 U.S. 304, 327–28, 327 n.19; Illinois v. City of

Milwaukee (“Milwaukee I”), 406 U.S. 91, 102–03, 102 n.3 (1972); New Jersey v. City of

New York, 283 U.S. 473, 477, 481–83 (1931); North Dakota v. Minnesota, 263 U.S. 365,

374 (1923); New York v. New Jersey, 256 U.S. 296 (1921); Georgia v. Tenn. Copper Co.,

21
206 U.S. 230 (1907); Missouri v. Illinois, 200 U.S. 496 (1906); Native Vill. of Kivalina v.

ExxonMobil Corp. (“Kivalina”), 696 F.3d 849, 855 (9th Cir. 2012); Illinois v. City of

Milwaukee (“Milwaukee III”), 731 F.2d 403, 406–11 (7th Cir. 1984); Texas v. Pankey, 441

F.2d 236, 240 (10th Cir. 1971)).

1. Milwaukee I

In Milwaukee I, the Supreme Court approved of the use of a public nuisance claim

under federal common law for a suit brought by Illinois against the City of Milwaukee and

other Wisconsin cities. 406 U.S. at 91. Illinois alleged that the cities were discharging 200

million gallons of raw or undertreated sewage into Lake Michigan in violation of Illinois

law. Id. at 93. Illinois asked the Court to exercise original jurisdiction over the matter and

abate the nuisance. Id. Although the Court declined to exercise original jurisdiction, it

allowed the action to proceed in the federal district court. Id. at 101, 108. The Court stated

that “[w]hen we deal with air and water in their ambient or interstate aspects, there is a

federal common law[.]” Id. at 103. The Court quoted the Tenth Circuit’s decision in Texas

v. Pankey for the following “controlling principle:”

As the field of federal common law has been given necessary expansion into
matters of federal concern and relationship (where no applicable federal
statute exists, as there does not here), the ecological rights of a State in the
improper impairment of them from sources outside the State’s own territory,
now would and should, we think, be held to be a matter having basis and
standard in federal common law and so directly constituting a question
arising under the laws of the United States.

Id. at 99–100 (quoting Pankey, 441 F.2d at 240).

The Court acknowledged that Congress had “enacted numerous laws touching

interstate waters[,]” id. at 101, but determined that “[t]he remedy sought by Illinois is not

22
within the precise scope of remedies prescribed by Congress[,]” id. at 103. “[I]n time,” the

Court presciently noted, “[i]t may happen that new federal laws and new federal regulations

may” preempt “the field of federal common law of nuisance.” Id. at 107. But until such a

time came to pass, the Court concluded, federal courts would be “empowered to appraise

the equities of the suits alleging creation of a public nuisance by water pollution.” Id.

2. Milwaukee II and Milwaukee III

Within months after the Milwaukee I decision, Congress passed the Clean Water

Act. The Supreme Court granted certiorari in Milwaukee II to consider the effect of the

Clean Water Act on the previously recognized federal common law nuisance cause of

action. 451 U.S. at 304.

In Milwaukee II, the Court began by recounting the litigation history that ensued

following its decision in Milwaukee I. Id. at 310–12. Illinois filed a complaint in the

federal district court, seeking abatement of the public nuisance that the Wisconsin cities

were allegedly creating by their discharges. Id. at 310. 11 While that litigation was pending,
10F

the Clean Water Act was enacted, and the EPA promulgated regulations concerning

specific effluent limitations that were required to be incorporated into discharge permits,

including the discharge permits applicable to the Wisconsin cities. Id. at 310–11. Pursuant

to the EPA’s delegation of authority under the Act, a Wisconsin state agency issued

discharge permits to the Wisconsin cities’ treatment plants. Id. at 311. The cities did not

11
The State of Michigan intervened in the federal common law nuisance suit,
seeking the same relief as Illinois. City of Milwaukee v. Illinois & Michigan (“Milwaukee
II”), 451 U.S. 304, 309 (1981).
23
comply with the permit requirements, and the state agency brought an enforcement action

in state court. Id. The state court entered a judgment requiring discharges from the cities’

treatment plants to meet the effluent limitations request set forth in the permits and

establishing a detailed timetable for completion of planning and additional construction to

control sewage overflows. Id.

In the meantime, the litigation in the Illinois nuisance suit was ongoing in the federal

district court. Id. Two months after the state court entered its judgment, the district court

rendered a decision finding that Illinois had proved the existence of a nuisance under

federal common law, arising from the Wisconsin cities’ discharges of both inadequate

treatment of its sewage, as well as from overflows. Id. The district court ordered the cities

to eliminate all overflows and to achieve the specified effluent limitations on treated

sewage. Id. The district court’s order also specified a construction timetable for the

completion of overflow facilities. Id. at 311–12. The conditions established by the district

court’s order in terms of overflows and effluent limitations went “considerably beyond”

the terms of the cities’ permits issued pursuant to the Clean Water Act and the state court’s

enforcement order. Id. at 312. The Wisconsin cities appealed. Id.

The Supreme Court held that the Clean Water Act displaced the federal common

law and that Illinois had no federal common law remedy available. The Court began by

explaining that the creation of federal common law was justified only when “Congress has

not spoken to a particular issue” and “there exists a significant conflict between some

federal policy or interest and the use of state law[.]” Id. at 313 (citation modified). The

Court stated that it has “always recognized that federal common law is subject to the

24
paramount authority of Congress.” Id. at 313 (citation modified). Because federal

common law “is a necessary expedient,” the Court explained, “when Congress addresses a

question previously governed by a decision rested on federal common law[,] the need for

such an unusual exercise of lawmaking by federal courts disappears.” Id. at 314 (citation

modified). The Court noted that this point was recognized in Milwaukee I, as well as in

Pankey, which was “the lower court decision extensively relied upon in that case[.]” Id. at

314.

In conducting its displacement analysis, the Court examined the legislative history

and the text of the Act and concluded that Congress’s clear intent was to establish an “all-

encompassing program of water pollution regulation.” Id. at 318. The Court explained

that the establishment of such a program—which did not exist when Milwaukee I was

decided—“strongly suggests that there is no room for courts to improve on that program

with the federal common law.” Id. at 319. Next, the Court analyzed the particular claims

at issue, which involved discharge effluent limitations, and noted that the problem of

effluent limitations had been “thoroughly addressed through the administrative scheme

established by Congress[.]” Id. at 319–20. The Court held that “[f]ederal courts lack

authority to impose more stringent effluent limitations under federal common law than

those imposed by the agency charged by Congress with administering this comprehensive

scheme.” Id. at 320. The Court did not view the overflow claims any differently, noting

that the permits specifically addressed the problem of overflows. Id. The Court also

pointed out that the enforcement action brought by the state agency in state court resulted

in a judgment that required the elimination of overflows by a certain date. Id. at 322.

25
Given the comprehensive regulatory scheme and the enforcement action that

addressed the effluent limitations and overflows, the Court stated that there was “no

‘interstice’ to be filled by federal common law[.]” Id. at 323. The Court explained that

“[a]lthough a federal court may disagree with the regulatory approach taken by the agency

with responsibility for issuing permits under the Act, such disagreement alone is no basis

for the creation of federal common law.” Id. The Court further concluded that the

“invocation of federal common law” by the lower federal courts “in the face of

congressional legislation supplanting it is peculiarly inappropriate in areas as complex as

water pollution control.” Id. at 325. The Court pointed out that the technical nature of the

subject matter was undoubtedly the reason that Congress “vested authority to administer

the Act in administrative agencies possessing the necessary expertise” and that the general

area was “particularly unsuited to the approach inevitable under” a federal common law

regime, which Congress had criticized as being “sporadic” and “ad hoc[.]” Id. Finally, the

Court observed that Congress provided ample opportunity for a state affected by a

neighboring state’s permitting agency to seek redress. Id. at 326. At bottom, the Court

concluded, Illinois’s basic grievance was that the permits issued to the cities did not impose

stringent enough controls on their discharges. Id. The Court rejected this argument as

presenting a valid basis for the imposition of federal common law. Id. The Court

concluded that “[i]t would be quite inconsistent” with Congress’s statutory scheme of

vesting permitting authority agencies with the necessary authority “if federal courts were

in effect to ‘write their own ticket’ under the guise of federal common law after permits

26
have already been issued and permittees have been planning and operating in reliance on

them.” Id.

Although the Court held that the federal legislation now occupied the field—thereby

displacing federal common law—the Court left open the question of whether injured

parties still had a cause of action under state law. Id. at 310 n.4. The case was remanded

for further consideration, which led to Milwaukee III.

In that case, Illinois filed a nuisance action against Milwaukee under Illinois

statutory and common law, seeking to abate the alleged pollution of Lake Michigan.

Illinois v. City of Milwaukee (“Milwaukee III”), 731 F.2d 403 (7th Cir. 1984). The Seventh

Circuit ultimately remanded the case for dismissal of Illinois’s claim, finding that the Clean

Water Act precluded the application of one state’s law against a pollution source located

in another state. Id. at 414. The decision was based in part on the court’s conclusion that

the application of different state laws to a single “point source” 12 would interfere with the
11F

carefully devised regulatory system established by the Clean Water Act. Id. The court

also concluded that the only suits that were not preempted were those alleging violations

of the laws of the polluting or “source” state. Id. at 413–14. As we discuss below, the

Seventh Circuit’s decision created a circuit split with the Second Circuit’s decision in

Ouellette.

12
A “point source” is defined by the Clean Water Act as “any discernible, confined
and discrete conveyance . . . from which pollutants are or may be discharged.” 33 U.S.C.
§ 1362(14).
27
3. Ouellette

In International Paper Company v. Ouellette, the Supreme Court considered

whether the Clean Water Act preempted a common law nuisance suit filed in the Vermont

federal district court under Vermont law when the source of the alleged injury was in New

York. 479 U.S. 481, 483 (1987). The suit was brought by property owners against a pulp

and paper mill company that discharged a variety of effluents into Lake Champlain. Id. at

483–84. The discharge pipe was located in New York and ended a short distance before

the state boundary line that divided the lake. Id. at 484. The property owners alleged that

the pollutants made the water “foul, unhealthy, smelly, and unfit for recreational use,”

thereby diminishing the value of their property. Id. (citation modified). The owners sought

$20 million in compensatory damages, $100 million in punitive damages, and injunctive

relief that would require the paper company to restructure part of its water treatment

system. Id.

The paper company moved to dismiss, claiming that the Clean Water Act preempted

the property owners’ state law claims. Id. Reaching a different conclusion than the

Seventh Circuit’s decision in Milwaukee III, the Vermont federal district court concluded

that the Clean Water Act did not preempt the state law nuisance claims. Id. at 485. The

court acknowledged that federal law normally governs interstate pollution, but it found that

two provisions of the Clean Water Act—§§ 510 and 505(e) 13 (together, the “saving
12F

13
The saving clause is contained in the original Clean Water Act as §§ 510 and 505.
Section 510 of the Clean Water Act, codified at 3 U.S.C. § 1370, provides: “Except as
expressly provided . . . , nothing in this chapter shall . . . be construed as impairing or in

28
clause”)—made it clear that federal law did not entirely preempt the states’ rights to control

pollution. Id. The district court held that a state action to redress interstate pollution was

not preempted, concluding that there was no interference with the Clean Water Act because

a state’s “imposition of compensatory damage award and other equitable relief merely

supplement[ed] the standards and limitations imposed by the Act.” Id. at 486–87 (citation

modified). The district court also found that the use of state law did not conflict with the

ultimate goal of the Clean Water Act, since the objective in each case was to decrease the

level of pollution. Id. at 487. The district court certified its decision for interlocutory

appeal, and the Second Circuit affirmed for the reasons stated by the district court. Id. The

Supreme Court granted certiorari “to resolve the circuit conflict on this important issue of

federal pre-emption.” Id.

The Supreme Court affirmed the denial of the paper company’s motion to dismiss,

but “reverse[d] the decision below to the extent it permit[ted] the application of Vermont

law to [the] litigation.” Id. The Court held “that when a court considers a state-law claim

concerning interstate water pollution that is subject to the” Clean Water Act, “the court

must apply the law of the state in which the point source is located.” Id.

The Court reviewed the evolution of federal law in the sphere of interstate water

pollution, including its decisions in Milwaukee I and Milwaukee II, and the enactment of

any manner affecting any right or jurisdiction of the States with respect to the waters
(including boundary waters) of such States.” Section 505(e), codified at 3 U.S.C. §
1365(e), states: “Nothing in this section shall restrict any right which any person (or class
of persons) may have under any statute or common law to seek enforcement of any effluent
standard or limitation or to seek any other relief[.]”
29
the Clean Water Act. In summarizing Milwaukee I, the Court stated that its “opinion in

that case affirmed the view that the regulation of interstate water pollution is a matter of

federal, not state, law[.]” Id. at 488. The Court explained that “Milwaukee I therefore held

that these cases should be resolved by reference to federal common law; the implicit

corollary of this ruling was that state common law was preempted.” Id. The Court

explained that Milwaukee I recognized that “future action by Congress to regulate water

pollution might pre-empt federal common law as well.” Id. The Court then discussed its

decision in Milwaukee II and its assessment that the Clean Water Act was a “complete

rewriting” of the statute considered in Milwaukee I, and the statutory provisions were “the

most comprehensive and far reaching” provisions that Congress had ever passed in that

area. Id. at 489 (citation modified) (citing Milwaukee II, 451 U.S. at 318–18). The Court

stated its holding in Milwaukee II that “federal legislation now occupied the field, pre-

empting all federal common law.” Id. (emphasis in original). The Court noted that

Milwaukee II “left open the question of whether injured parties still had a cause of action

under state law.” Id. That window, noted the Court, resulted in the remand and decision

of the Seventh Circuit in Milwaukee III.

The Court observed that the Clean Water Act recognizes that states “should have a

significant role in protecting their own natural resources[,]” id., pointing out the provisions

of the Act that allow the federal government to delegate to the state the authority to

administer the NPDES program with respect to point sources in the state, and the state’s

ability to require discharge limitations more stringent than those required by the federal

government, id. at 490. The Clean Water Act, explained the Court, “establishes a

30
regulatory partnership” between the federal government and the source state. Id. (citation

modified).

By contrast, the Court explained that the Act “contemplates a much lesser role for

States that share an interstate waterway with the source (the affected States).” Id. The

Court observed that “[e]ven though it may be harmed by discharges, an affected State only

has an advisory role in regulating pollution that originates beyond its borders.” Id. The

Court noted that the affected state does not have the authority to block the issuance of the

permit if it is dissatisfied with the proposed standards, nor may it establish a separate permit

system to regulate an out-of-state source. Id. at 491. The Court concluded that the “Act

makes it clear that affected States occupy a subordinate position to source States in the

federal regulatory program.” Id.

Turning to the question presented—“whether the Act pre-empts Vermont common

law to the extent that law may impose liability on a New York point source[]”—the Court

began its analysis by stating the standards governing a court’s consideration whether a

federal statute preempts state law: (1) “that it is not necessary for a federal statute to provide

explicitly that particular state laws are pre-empted”; (2) preemption “may be presumed

when the federal legislation is sufficiently comprehensive to make reasonable the inference

that Congress left no room for supplementary state regulation”; and (3) “in addition to

express or implied pre-emption, a state law also is invalid to the extent that it actually

conflicts with a federal statute” and that “such a conflict will be found when the state law

stands as an obstacle to the accomplishment and execution of the full purposes and

objectives of Congress.” Id. at 491–92 (citation modified).

31
The Court determined that “[a]lthough Congress intended to dominate the field of

pollution regulation, the saving clause negate[d] the inference that Congress left no room

for state causes of action.” Id. at 492. Examining the plain text of the saving clause, as

well as the Act as a whole, its purposes and legislative history, the Court concluded that if

“affected States were allowed to impose separate discharge standards on a single point

source, the inevitable result would be a serious interference with the achievement of the

full purposes and objectives of Congress.” Id. at 493–94 (citation modified). Determining

that Congress did not intend to “undermine this carefully drawn statute through a general

saving clause,” the Court concluded that the Clean Water Act “precludes a court from

applying the law of an affected State against an out-of-state source.” Id. at 494 (citation

modified).

The Court next turned to the issue of “whether Vermont nuisance law stands as an

obstacle to the full implementation of the [Act],” explaining that “it is not enough to say

that the ultimate goal of both federal and state law is to eliminate water pollution.” Id.

(citation modified). The Court stated that a “state law also is pre-empted if it interferes

with the methods by which the federal statute was designed to reach this goal.” Id. The

Court determined that the application of Vermont law against the paper company would

allow the property owners “to circumvent the NPDES permit system, thereby upsetting the

balance of public and private interests so carefully addressed by the Act.” Id. Specifically,

the Court pointed out, the Clean Water Act envisions a balancing of interests between the

goal of the elimination of water pollution, and “competing public and industrial uses,”

while also taking into account technological feasibility. Id. at 494–95.

32
The Court concluded that “[a]n interpretation of the saving clause that preserved

actions brought under an affected State’s law would disrupt this balance of interests.” Id.

at 495. 14 The Court determined that “[a]pplication of an affected State’s law to an out-of-
13F

state source” would also “undermine the important goals of efficiency and predictability in

the permit system.” Id. at 496. The Court observed that the property owners’ interpretation

of the saving clause would subject a source to “a variety of common-law rules established

by the different States along interstate waterways[]” and noted that “[t]hese nuisance

standards often are vague and indeterminate.” Id. (citation modified). Moreover, the Court

14
The Court further elucidated the problem with such an interpretation as follows:

If a New York source were liable for violations of Vermont law, that law
could effectively override both the permit requirements and the policy
choices made by the source State. The affected State’s nuisance laws would
subject the point source to the threat of legal and equitable penalties if the
permit standards were less stringent than those imposed by the affected State.
Such penalties would compel the source to adopt different control standards
and a different compliance schedule from those approved by the EPA, even
though the affected State had not engaged in the same weighing of the costs
and benefits. This case illustrates the problems with such a rule. If the
Vermont court ruled that [the property owners] were entitled to the full
amount of damages and injunctive relief sought in the complaint, at a
minimum [the paper company] would have to change its methods of doing
business and controlling pollution to avoid the threat of ongoing liability. In
suits such as this, an affected-state court also could require the source to cease
operations by ordering immediate abatement. Critically, these liabilities
would attach even though the source had complied fully with its state and
federal permit obligations. The inevitable result of such suits would be that
Vermont and other States could do indirectly what they could not do
directly—regulate the conduct of out-of-state sources.

Int’l Paper Co. v. Ouellette, 479 U.S. 481, 495 (1987).
33
pointed out that “[t]he application of numerous states’ laws would only exacerbate the

vagueness and resulting uncertainty.” Id.

The Court stated that Congress, through the Clean Water Act, “carefully defines the

role of both the source and affected States,” and that the “delineation of authority represents

Congress’s considered judgment as to the best method of serving the public interest and

reconciling the often competing concerns of those affected by the pollution.” Id. at 497.

The Court concluded that “[i]t would be extraordinary for Congress, after devising an

elaborate permit system that sets clear standards, to tolerate common-law suits that have

the potential to undermine this regulatory structure.” Id.

Although the Court held that the Clean Water Act preempted the application of

Vermont’s nuisance common law to a New York point source, the Court stated that did not

mean that the property owners did not have a remedy. Id. The Court pointed out that the

“saving clause specifically preserves other state actions, and therefore nothing in the Act

bars aggrieved individuals from bringing a nuisance claim pursuant to the law of the source

State.” Id. (emphasis in original). The Court noted that the Clean Water Act allows states

to impose higher standards and higher statutory restrictions, which preserve common-law

suits applying the laws of the source state. Id. at 498. The Court determined that such an

interpretation of the saving clause would not frustrate the goal of the Act. First, the Court

explained, it would not “disturb the balance among federal, source-state and affected state

interests.” Id. at 499. Second, the Court reasoned, “restriction of suits to those brought

under source-state nuisance law prevents a source from being subject to an indeterminate

number of potential regulations.” Id. Moreover, the Court stated that “States can be

34
expected to take into account their own nuisance laws in setting permit requirements.” Id.

The Court concluded that the Clean Water Act “pre-empts state law to the extent that the

state law is applied to an out-of-state point source.” Id. at 500.

4. American Electric Power Co., Inc. v. Connecticut (“AEP”)

All of the above cases involved water pollution. AEP involved air emissions and

claims concerning global warming. 564 U.S. at 410. In that case, eight states, New York

City, and three private land trusts brought a public nuisance suit under federal common law

against the five largest emitters of carbon dioxide in the United States. Id. at 418. The

plaintiffs sought to redress those emitters’ “contribut[ions] to global warming[.]” Id. In

terms of relief, they sought an injunction “requiring each defendant to cap its carbon

dioxide emissions and then reduce them by a specified percentage each year for at least a

decade.” Id. at 419 (citation modified). Determining that the Clean Air Act already

“provides a means to seek limits on emissions of carbon dioxide from domestic power

plants[,]” the Supreme Court held that the Clean Air Act “displaces any federal common-

law right to seek abatement of” greenhouse gas emissions. Id. at 424.

The Court started its discussion by pointing out that, in Massachusetts v. EPA, it

held that the Clean Air Act authorizes federal regulation of carbon dioxide and other

greenhouse gases. Id. at 416. The Court noted that following its decision in Massachusetts,

the EPA undertook greenhouse gas rulemaking efforts. Id. at 416–18. The Court held

“that the Clean Air Act and the EPA actions it authorizes displace any federal common-

law right to seek abatement of carbon-dioxide emissions from fossil-fuel fired

powerplants.” Id. at 424.

35
In so holding, the Court touched upon the regulatory framework of the Act,

including the authority vested in the EPA to identify categories of stationary sources that

“caus[e], or contribut[e] significantly to, air pollution, which may reasonably be anticipated

to endanger public health or welfare.” Id. (quoting 42 U.S.C. § 7411(b)(1)(A)). The Court

also pointed out that the “Act provides multiple avenues for enforcement[]” and

summarized the various statutory mechanisms for enforcement. Id. at 425.

In determining that the Clean Air Act displaced the application of federal common

law, the Court noted that Congress, through the Clean Air Act, designed the EPA as the

“expert agency” to undertake complex balancing of interests involving greenhouse gas

emissions, stating:

The appropriate amount of regulation in any particular greenhouse gas-
producing sector cannot be prescribed in a vacuum: As with other questions
of national or international policy, informed assessment of competing
interests is required. Along with the environmental benefit potentially
achievable, our Nation’s energy needs and the possibility of economic
disruption must weigh in the balance.

Id. at 427. The Court commented on the difficulties presented by district court judges

lacking the “scientific, economic, and technological resources an agency can utilize in

coping with issues of this order.” Id. at 428. The Court concluded that having individual

federal judges determine in the first instance what amount of carbon dioxide emissions is

unreasonable, and then decide what level of reduction is “practical, feasible, and

economically viable,” in not only the underlying case, but also in numerous other cases,

could not “be reconciled with the decisionmaking scheme Congress enacted.” Id. at 428–

29.

36
Finally, the Court noted that the plaintiff also sought relief under state laws and

pointed out that the Second Circuit had addressed those claims because it held that federal

common law governed. Id. at 429. In light of its “holding that the Clean Air Act displaces

federal common law” and citing to Ouellette, the Court stated that “the availability vel non

of a state lawsuit depends, inter alia, on the preemptive effect of the federal Act.” Id. The

Court quoted that portion of the Ouellette holding that the Clean Water Act does not

preclude aggrieved individuals from bringing “a nuisance claim pursuant to the law of the

source State[.]” Id. (quoting Ouellette, 479 U.S. at 489). Because “[n]one of the parties

have briefed preemption or otherwise address the availability of a claim under state

nuisance law[,]” the Court left “the matter open for consideration on remand.” Id.

Although the United States Supreme Court has not addressed whether the Clean Air

Act preempts state law claims for damages against gas, oil, and energy companies for

injuries related to greenhouse gas emissions, lower federal courts have concluded that such

claims are preempted.

5. Native Village of Kivalina v. ExxonMobil Corp.

In Native Village of Kivalina v. ExxonMobil Corporation, a small city in Alaska

brought a public nuisance action under federal common law against numerous oil, energy,

and utility companies for their emissions of greenhouse gases. 696 F.3d 849, 854 (9th Cir.

2012). Unlike in AEP, the plaintiff did not seek abatement of emissions, but rather,

damages for global warming-related injuries, including sea-level rise and severe erosion.

Id. at 853.

37
Despite the difference in remedies, the United States Court of Appeals for the Ninth

Circuit concluded that AEP controlled. The court reasoned that the displacement of federal

common law does not turn on the nature of the remedy, but instead, on the cause of action.

Id. at 856–57 (noting that the “Supreme Court has instructed that the type of remedy

asserted is not relevant to the applicability of the doctrine of displacement”).

6. City of New York v. Chevron Corp.

In City of New York v. Chevron Corporation, the City of New York filed a lawsuit

in federal court, asserting state common law causes of action for public nuisance, private

nuisance, and trespass against five oil companies stemming from the companies’

production, promotion, and sale of fossil fuels around the world. 993 F.3d 81, 88 (2d Cir.

2021). The city sought compensatory damages for past and future costs of climate-

proofing its infrastructure and property, as well as an equitable order ascertaining damages

and granting an injunction to abate the public nuisance and trespass that would go into

effect should the companies fail to pay the court-ordered damages. Id. The companies

filed motions to dismiss the city’s complaint. Id. The district court granted the motions

and dismissed the city’s complaint. Id. After the city appealed, the United States Court of

Appeals for the Second Circuit affirmed. Id. at 88, 86.

The court held that the city could not maintain a nuisance suit seeking to recover

damages for harms caused by global greenhouse gas emissions under New York law. Id. at

91. The court observed that the city was requesting damages for the cumulative impact of

conduct occurring simultaneously across just about every jurisdiction on the planet. Id. at 92–

93. The court determined that “[s]uch a sprawling case is simply beyond the limits of state

38
law[,]” in part because a substantial damages award like the one requested by the city would

effectively regulate the producers’ behavior far beyond New York’s borders. Id. at 92.

As an initial matter, the court rejected the city’s attempt to characterize its complaint

as “merely a local spat about the City’s eroding shoreline, which will have no appreciable

effect on national energy or environmental policy.” Id. at 91. The court determined that

“[a]rtful pleading” could not “transform the City’s complaint into anything other than a

suit over global greenhouse gas emissions.” Id. In other words, explained the court, “it

[was] precisely because fossil fuels emit greenhouse gases—which collectively exacerbate

global warming—that the city [wa]s seeking damages.” Id. (citation modified). The court

concluded that a substantial damages award like the one requested by the city would

effectively regulate the producers’ behavior far beyond New York’s borders. Id. at 92–93

(citing Kurns v. R.R. Friction Prods. Corp., 565 U.S. 625, 637 (2012)). Indeed, the Second

Circuit concluded, the goal of the city’s lawsuit was “perhaps even more ambitious” than

imposing emission regulations—the city was effectively attempting to “impose strict

liability for the damages caused by fossil fuel emissions no matter where in the world those

emissions were released (or who released them).” Id. at 93. The court concluded that the

city’s claims could not be brought under state law, and any claims must arise under federal

common law.

Having determined that any claims made by the city must arise under the federal

common law, the Second Circuit next determined that under AEP, the Clean Air Act

displaced federal common law nuisance suits seeking to abate domestic transboundary

emissions of greenhouse gases. Id. at 95. The court also agreed with the Ninth Circuit’s

39
reasoning in Kivalina and held that the Clean Air Act also displaces the city’s common law

damages claims. Id. at 96.

The court next addressed the city’s argument that if the Clean Air Act displaced

federal common law, then the city’s state law nuisance claims may “snap back into action”

unless specifically preempted by statute. Id. at 98. The court summarized the city’s view

of the Clean Air Act “as having vaporized any preemptive effect that federal common law

had on state law, thereby requiring us to engage in a traditional statutory preemption

analysis.” Id. The court stated that “the City’s position is difficult to square with the fact

that the federal common law governed this issue in the first place.” Id. The court pointed

out that under Supreme Court precedent, where a federal statute displaces federal common

law, it does so in a field in which states have not traditionally occupied. Id. (citing Boyle,

487 U.S. at 507). “Consequently,” the Second Circuit reasoned, “state law does not

suddenly become presumptively competent to address issues that demand a unified federal

standard simply because Congress saw fit to displace a federal court-made standard with a

legislative one[.]” Id.

Recognizing that Congress could grant states the authority to operate in an area of

national concern, the court turned to the text of the Clean Air Act and concluded that the

Act does not authorize the type of state law claims the city sought to prosecute. Id. at 99.

The court determined that among the Act’s expansive set of enforcement mechanisms, the

only provisions that might plausibly authorize the type of state law claims pursued by the

40
city were the provisions that constitute the saving clause, 42 U.S.C. §§ 7604(e) and 7416. 15
14F

Id. The court concluded that, like the nearly identical saving clause in the Clean Water

Act, the saving clause in the Clean Air Act, “plainly permit[s] states to create and enforce

their own emissions standards applicable to in-state polluters[.]” Id. Returning to the city’s

claims as they applied to domestic conduct, the court concluded that they did not fall within

the “slim reservoir of state common law.” Id. at 100.

Finally, the Second Circuit turned to the city’s claims that concerned foreign

emissions. Id. The court noted that the Clean Air Act’s “silence on the issue of

extraterritorial reach, the fact that the Act contemplates the need for reciprocal protections

from foreign nations, and the State Department’s lead role in setting foreign policy on

environmental matters, all plainly demonstrate the Clean Air Act regulates only domestic

emissions.” Id. at 101. As a result, the court reasoned, the Clean Air Act could not displace

the city’s federal common law claims to the extent that they seek recovery for harms caused

by foreign emissions. Id. That said, the court stated that “foreign policy concerns foreclose

New York’s proposal here to recognize a federal common law cause of action targeting

emissions emanating from beyond our national borders.” Id.

The court determined that extending the federal common law to address claims

relating to foreign emissions would trigger “broad concerns over separation of powers,

intrusion on the political branches’ monopoly over foreign policy, and judicial caution with

respect to creating (or extending) federal common law causes of action.” Id. at 102. The

15
We discuss the Clean Air Act’s saving clause in more detail in our analysis below.
41
court concluded that holding producers accountable for purely foreign activity would

require them to internalize the costs of climate change, which would “presumably affect

the price and production of fossil fuels abroad.” Id. at 103. The court also pointed out that

it would “bypass the various diplomatic channels that the United States uses to address this

issue, such as the U.N. Framework and the Paris Agreement.” Id. “Such an outcome,” the

court reasoned, “would obviously sow confusion and needlessly complicate the nation’s

foreign policy, while clearly infringing on the prerogatives of the political branches.” Id.

The court further determined that “condoning an extraterritorial nuisance action here would

not only risk jeopardizing our nation’s foreign policy goals but would also seem to

circumvent Congress’s own expectations and carefully balanced scheme of international

cooperation on a topic of global concern.” Id. The Second Circuit agreed with the district

court that “any federal common law claim against the [p]roducers that is not displaced by

the Clean Air Act” fails given “the need for judicial caution in the face of delicate foreign

policy considerations.” Id.

Against the backdrop of these federal cases, we turn to the state law claims asserted

by the local governments in the cases before us.

V

Federal Displacement/Preemption Analysis

A. Baltimore’s State Tort Claims Are Displaced by Federal Common Law

As reflected in the above survey of cases, for more than a century, the Supreme

Court and lower federal courts have held that interstate pollution is an inherently federal

area necessarily governed by federal law. See Int’l Paper Co. v. Ouellette, 479 U.S. 481,

42
488 (1987) (stating that “the regulation of interstate water pollution is a matter of federal,

not state, law”); AEP, 564 U.S. at 421, 422 (reiterating that “air and water in their ambient

or interstate aspects” are “meet for federal law governance”); City of New York, 993 F.3d

at 91 (collecting cases); Kivalina, 696 F.3d at 855 (stating that “[p]ost-Erie, federal

common law includes the general subject of environmental law and specifically includes

ambient or interstate air and water pollution”); Pankey, 441 F.2d at 240 (explaining that

the impairment of the ecological rights of a state from sources outside the state’s own

territory is a “matter having basis and standard in federal common law” and “constituting

a question arising under the laws of the United States”); Kansas v. Colorado, 206 U.S. 46,

97 (1907) (explaining that allowing the law of one state to govern disputes regarding

pollution emanating from another would violate the “cardinal” principle that “[e]ach State

stands on the same level with all the rest[,]” by permitting one state to impose its laws on

another state and its citizens). Federal law governs such controversies because they

“touch[] basic interests of federalism[]” and implicate a “uniform rule of decision[.]”

Milwaukee I, 406 U.S. at 105 n.6. And because “borrowing the law of a particular State

would be inappropriate[]” to resolve such interstate disputes, federal law must govern.

AEP, 564 U.S. at 422.

Given that federal law governs claims alleging injuries caused by interstate and

international emissions, we start by asking whether the local governments’ state law

43
claims, in fact, involve the regulation of interstate pollution and are therefore permitted,

if at all, only under federal law. 16 The answer is yes. 17
15F 16F

16
The circuit courts below, as well as the Defendants and their amici, the United
States, and 24 states, explained in support of their position that the inapplicability of state
law to injuries allegedly caused by interstate and international emissions arises from the
structure of the United States Constitution. Given that federal common law originates from
principles of federalism and is developed to address a uniquely federal interest where state
law is not applicable, we agree. See AEP, 564 U.S. at 421 (explaining that “federal common
law addresses subjects within national legislative power where Congress has so directed or
where the basic scheme of the Constitution so demands”) (emphasis added); Boyle v. United
Techs. Corp., 487 U.S. 500, 504 (1988) (observing that there are some areas involving
uniquely federal interests that “are so committed by the Constitution . . . to federal control
that state law is preempted”); cf. Franchise Tax Bd. of Cal. v. Hyatt, 587 U.S. 230, 246
(2019) (explaining that the federal “Constitution implicitly forbids” states from applying
their own law to certain matters “because the interstate nature of the controversy makes it
inappropriate for state law to control”) (citation modified). Such exclusively federal areas
include “interstate and international disputes implicating the rights of States or our relations
with foreign nations” and “areas in which a federal rule of decision is necessary to protect
uniquely federal interests.” Tex. Indus., 451 U.S. at 641–42. Although we undertake a
federal displacement/preemption analysis through the framework applied in Ouellette and
City of New York, we agree with the Defendants and their amici that the development of
federal common law is rooted in the same federalism principles that underpin the structure
of the United States Constitution.
17
We pause for a moment to recognize that, at first blush, our conclusion may
appear to be at odds with the United States Court of Appeals for the Fourth Circuit’s
analysis of Baltimore’s claims in the removal context. See Mayor & City Council of Balt.
v. BP P.L.C., 31 F.4th 178, 214, 216 (4th Cir. 2022) (concluding that Baltimore’s claims
“do not involve the regulation of emissions” and do not “disturb foreign relations”). The
court acknowledged, however, that the Defendant’s alleged deception mattered only
insofar as it “drove consumption, and thus climate change.” Id. at 234.

Our analytical lens is different from that applied by the Fourth’s Circuit in the
removal context, which required it to apply a “heightened standard unique to the
removability inquiry” to determine whether Baltimore’s state law actions arose under
federal law. Id. at 203. The issue before the Fourth Circuit was whether the Defendants’
anticipated defenses could singlehandedly create federal question jurisdiction under 28
U.S.C. § 1331 in light of the well-pleaded complaint rule. Id. at 197–98; see Caterpillar
Inc. v. Williams, 482 U.S. 386, 398 (1987) (noting that “the fact that a defendant might

44
The beginning point for our federal displacement/preemption inquiry is whether

the local governments’ claims in which they seek damages for alleged impacts of climate

change, is tantamount to regulation of interstate or international pollution as the

Defendants assert, or whether the claims are limited to deceptive and misleading

commercial conduct that lies within the “core” of the local governments’ state police

powers, as argued by the local governments.

At the outset, we observe that the local governments’ claims are similar to New

York’s claims that the Second Circuit analyzed in City of New York, 993 F.3d 81. Like

New York, the local governments allege that the Defendants “have known for decades

ultimately prove that a plaintiff’s claims are preempted under [federal law] does not
establish that they are removable to federal court” (citation modified)). “A plaintiff’s
complaint ‘may not be removed to federal court on the basis of a federal defense, including
the defense of pre-emption, even if the defense is anticipated in the plaintiff’s complaint,
and even if both parties concede that the federal defense is the only question truly at issue.’”
Baltimore, 31 F.4th at 198 (quoting Caterpillar, 482 U.S. at 393).

Relatedly, the Fourth Circuit was required to determine whether the doctrine of
complete preemption applied, which is a recognized exception to the well-pleaded
complaint rule. Id. Complete preemption is a jurisdictional doctrine that has the effect of
transforming a state law cause of action into one arising under federal law because
Congress has occupied the field so thoroughly as to leave no room for state law causes of
action at all. Id. By contrast, ordinary preemption—one of the defenses asserted before
this Court—“is not a jurisdictional doctrine because it simply declares the primacy of
federal law, regardless of the forum or the claim.” Id. (citation modified).

The Fourth Circuit ultimately concluded that the face of Baltimore’s complaint did
not raise claims under federal common law. Id. at 200–07. The court made it clear that
the Defendants’ merits-based ordinary preemption defense was reserved for the state court
on remand. Id. at 198–99. Because the court was concerned only with removal jurisdiction
and the application of complete preemption, it did not “delve into the[] defenses at
Defendants’ disposal[,]” including ordinary preemption. Id. at 198 n.2. Those issues, of
course, are before this Court.
45
that their fossil fuel products pose a severe risk to the planet’s climate[]” but “downplayed

the risks and continued to sell massive quantities of fossil fuels, which has caused and will

continue to cause significant change to [plaintiffs’] climate and landscape.” City of New

York, 993 F.3d at 86–87. The local governments assert that the Defendants are

“responsible for global warming and should bear the brunt of these costs[]” even though

“every single person who uses gas and electricity . . . contributes to global warming[].”

993 F.3d at 86.

We reject the local governments’ narrow reading of their complaints to suggest that

they only seek redress for “deceptive and misleading commercial conduct” within the

sphere of their local powers and authority. As noted above, the local governments allege

that the Defendants substantially contributed to greenhouse gas pollution, global warming,

and climate change by extracting, producing, promoting, refining, marketing, distributing,

and selling fossil fuel products (i.e., coal, oil, and natural gas). The claims are not limited

to deceptive and misleading commercial conduct.

Even assuming that the claims were limited to allegations of deceptive and

misleading marketing, we reject the assertion that their sweeping claims may be pursued

under state law. Although we are required to view the local governments’ allegations in

the light most favorable to them, we are not required to defer to their characterization of

the nature of their claims. No amount of creative pleading can masquerade the fact that

46
the local governments are attempting to utilize state law to regulate global conduct that is

purportedly causing global harm. 18
17F

Assuming the truth of the local governments’ allegations, they claim that the

Defendants engaged in worldwide conduct—which allegedly inflated fossil fuel

consumption, increased greenhouse gas emissions, accelerated global warming, and

thereby created hazardous conditions in Baltimore, Annapolis, and Anne Arundel

County—including sea-level rise, flooding, storm surges, and heat waves. Put another

way, the local governments allege that the Defendants engaged in worldwide deception

and caused worldwide injuries in the form of cumulative emissions. The local

governments cannot escape this inescapable conclusion: they are seeking to apply

Maryland law to regulate conduct that occurs outside their jurisdictional borders, as well

as within the State’s borders. The local governments’ police powers do not extend beyond

their respective borders, and certainly do not authorize the policing of global conduct.

The nature and scope of the damages sought by the local governments further

reflect that their claims seek to regulate conduct outside Maryland that is causing global

18
We respectfully disagree with the Supreme Courts of Hawaii and Colorado in
their analysis of similar claims and in their conclusion that such claims do not seek to
regulate emissions or seek damages for interstate emissions. City & County of Honolulu
v. Sunoco LP, 537 P.3d 1173, 1181 (Haw. 2023), cert. denied, 145 S. Ct. 1111 (2025) (No.
23-947); County Comm’rs of Boulder County v. Suncor Energy USA, Inc. (“Boulder”), No.
24SA206, 2025 WL 1363355, at *10 (Co. 2025), cert. granted, ___S. Ct. ___, 2026 WL
490537 (2026) (No. 25-170). Our view of the claims here aligns with the dissent in the
Boulder case. See Boulder, 2025 WL 1633355, at *13, *16 (“While Boulder’s state law
claims masquerade as tort claims for damages, a closer look at the substance of those
claims’ allegations reveals that Boulder seeks to effectively abate or regulate interstate
emissions,” which “state law remains incompetent” to do.) (Samour, J., dissenting).
47
warming. The local governments seek damages for injuries “caused by anthropogenic

greenhouse gas emissions,” which are “all due to anthropogenic global warming.” To

state the obvious, global warming is created by global consumption. Given that Maryland

accounts for only a fraction of global carbon dioxide emissions, 19 Maryland’s emissions
18F

alone cannot possibly be responsible for causing the local governments’ alleged injuries.

In other words, if the Defendants had labeled their products differently in Maryland to

warn Marylanders about the dangers of fossil fuel consumption, and every human,

government, corporation, or other entity that consumes fossil fuels every day heeded those

warnings, it would have been but a drop in the bucket in terms of the effects of greenhouse

gas pollution, global warming, or climate change. Viewing the allegations of the

complaint in the light most favorable to the local governments, they are necessarily

seeking damages for harms attributed to all interstate and international emissions

combined—plain and simple. Baltimore mentions “emissions” 115 times in its complaint.

The local governments cannot, in one breath, disavow any intent to address interstate and

global emissions, and in another, identify such emissions as the single source of their

harms.

As of 2023, the United States is responsible for 11% of global greenhouse gas
19

emissions. Ctr. for Climate and Energy Sol., Global Emissions: Greenhouse Gas
Emissions by Top Emitters, 2023, https://perma.cc/7V6E-G6HQ. Maryland’s carbon
dioxide emissions represent less than 0.1% of the nation’s carbon emissions. U.S. Energy
Info. Admin., Energy Related CO2 Emission Data Tables, Table 1 (2023),
https://perma.cc/P73Q-UG97. Maryland’s emissions constitute a small percentage of the
United States’ emissions, let alone the globe’s.
48
We agree with the Second Circuit that “[s]uch a sprawling case is simply beyond

the limits of state law.” City of New York, 993 F.3d at 92. A substantial damages award

like the ones the local governments seek would effectively regulate the Defendants’

behavior far beyond Maryland’s borders. Because greenhouse gases, once emitted,

become well mixed in the atmosphere, AEP, 564 U.S. at 422, they cannot be traced to

their source, as they quickly diffuse and comingle in the atmosphere. City of New York,

993 F.3d at 92. Any actions that the Defendants take to mitigate their liability in

Baltimore, Annapolis, and the County will undoubtedly have a significant impact across

every state and country. One cannot isolate these local governments’ claims from the

continuum of the harmful effects of global warming on the entire planet. Addressing the

local governments’ alleged injury requires the application of Maryland law to out-of-state

and international conduct. Indeed, the fact that the United States and 24 states 20 have filed
19F

amicus briefs in support of the Defendants “aptly illustrates that this is an interstate matter

raising significant federalism concerns.” Id.

The local governments once again attempt to recast the sweeping scope of their

lawsuit by pointing out that they are not “asking the court to enjoin or reduce fossil-fuel

production or emissions.” We are unpersuaded by the local governments’ myopic view

of their claims or their attempt to ignore or minimize the effect that a significant damages

award would have on both domestic and international attempts to regulate pollution—

The states of Alabama, Alaska, Arkansas, Florida, Georgia, Idaho, Indiana, Iowa,
20

Kansas, Kentucky, Louisiana, Mississippi, Missouri, Montana, Nebraska, North Dakota,
Ohio, Oklahoma, South Carolina, South Dakota, Texas, Utah, West Virginia, and
Wyoming filed an amicus brief in support of the Defendants.
49
matters which are solely within the purview of federal law. That these local governments

are seeking damages—as opposed to injunctive relief related to the imposition of pollution

standards—does not alter our conclusion. As the Supreme Court has recognized,

“‘regulation can be effectively exerted through an award of damages,’ and ‘the obligation

to pay compensation can be, indeed is designed to be, a potent method of governing

conduct and controlling policy.’” Kurns v. R.R. Friction Prods. Corp., 565 U.S. 625, 637

(2012) (citation modified) (quoting San Diego Bldg. Trades Council v. Garmon, 359 U.S.

236, 247 (1959)); see also BMW of N. Am., Inc. v. Gore, 517 U.S. 559, 572, n.17 (1996)

(observing that “[s]tate power” can be wielded as much by the “application of a state rule

of law in a civil lawsuit as by a statute[]” and explaining that “principles of sovereignty

and comity” mean “that a [s]tate may not impose economic sanctions on violators of its

laws with the intent of changing the tortfeasors’ lawful conduct in other States”).

Environmental tort claims force defendants “to change [their] methods of doing

business[.]” Ouellette, 479 U.S. at 495. Clearly, the local governments are seeking to

impose damages on the Defendants for injuries allegedly caused by the effect of interstate

and international greenhouse gas emissions on global climate change. As a result, the

local governments’ claims fall squarely within the inherently federal areas of interstate

pollution and foreign affairs and may therefore only be brought under federal law.

Allowing each of the 50 states (and the countless individual local governments

located within them) to impose their own preferred policy solutions for climate change—

with each state naturally focused on local rather than national or international impacts,

would create a plainly “irrational system of regulation” that would lead to “chaotic

50
confrontation between sovereign states.” Ouellette, 479 U.S. at 496 (citation modified);

see also City of New York, 993 F.3d at 93 (observing that “states will invariably differ

in their assessment of the proper balance between . . . national and international

objectives”). We agree with the Second Circuit’s conclusion that “to permit th[ese]

suit[s] to proceed under state law would further risk upsetting the careful balance that

has been struck between the prevention of global warming, a project that necessarily

requires national standards and global participation on the one hand, and energy

production, economic growth, foreign policy, and national security, on the other.” City

of New York, 993 F.3d at 93; see also AEP, 564 U.S. at 427; 43 U.S.C. § 1802(1)

(declaring that some regulatory goals of promoting oil and natural gas resource

management policies are “to achieve national economic and energy policy goals, assure

national security, reduce dependence on foreign sources, and maintain a favorable

balance of payments in world trade”). We therefore conclude that any state law claims

are displaced by federal common law. 2120F

21
It is an understatement to say that we view the allegations set forth in the local
governments’ complaints—and the analytical framework that follows therefrom—
differently from the dissent. We briefly explain these differences here.

The dissent asserts that the local governments have brought a “fraud case, and the
CAA has nothing to say about fraud.” Dissenting Slip. Op. at *4. According to the dissent,
the “local injuries” for which the local governments seek damages are “caused by local
impacts of a global phenomenon, and they are alleged to have resulted from a fraud, not
from an emissions policy.” Id. at *5. The dissent posits that because this case alleges a
fraud, the local governments’ claims arise from the “state’s historic police powers,” and
therefore, we must apply a preemption framework to the local governments’ claims in a
manner similar to cases such as Virginia Uranium, Inc. v. Warren, 587 U.S. 761 (2019);
Altria Group, Inc. v. Good, 555 U.S. 70 (2008); and Cipollone v. Liggett Group, Inc., 505

51
U.S. 504 (1992). Dissenting Slip. Op. at **2, 7, 19–22, 33–38, 48, 50, 53, 73. These cases,
of course, did not involve interstate pollution. See Va. Uranium, 587 U.S. at 761 (holding
that the Federal Atomic Energy Act did not preempt Virginia’s ban on uranium mining);
Altria Group, Inc., 555 U.S. 70; Cipollone, 505 U.S. at 504 (holding in each case that the
Federal Cigarette Labeling and Advertising Act did not preempt state law claims brought
against tobacco and cigarette manufacturers).

The dissent’s reliance on these cases flows from the fact that the dissent does not
view the local governments’ claims as pertaining to or affecting interstate emissions, and
therefore, the dissent determines that the Supreme Court’s analytical framework applied in
Ouellette has no application. The dissent also contends that we have “conflate[d]
displacement and preemption[,]” which the dissent states are “distinct doctrines with
distinct standards and distinct consequences.” Dissent Slip. Op. at *48–49.

Of course, as our opinion reflects, we disagree with the dissent’s characterization
of the local governments’ claims, and the analytical framework that the dissent argues is
applicable here. First, we disagree with the dissent that the claims relate only to fraud or
deceptive marketing claims arising under state common law and that the claims are within
the local governments’ “traditional police powers.” We will not repeat our reasoning or
analysis here other than to reiterate that the local governments are clearly attempting to
utilize state law to address global conduct that is purportedly causing global harm. The
ultimate conduct is the use of greenhouse gases across the globe, and the ultimate harm
asserted by the local governments arises from global emissions. The local governments’
police powers do not extend beyond their respective borders and certainly do not
authorize the policing of worldwide conduct. We simply do not view the local
governments’ claims in the same manner as the dissent or as the high courts of Hawaii
and Colorado. Rather, our analysis aligns with the dissent from the high court of
Colorado in Boulder, 2025 WL 1363355, at *12, and the Second Circuit in City of New
York, 993 F.3d at 98.

Second, because we determine that the local governments, through their state law
claims, are attempting to address air emissions, the correct analytical framework is to
consider the claims through the lens of federal law—which is the same framework that
the Second Circuit applied to similar claims in the City of New York. That is, we
recognize that historically, claims involving interstate pollution arose under federal
common law, which displaced state law. See AEP, 564 U.S. at 421, 422. With the
enactment of the Clean Air Act, federal common law claims, in turn, were displaced by
that federal statute. See id.; City of New York, 993 F.3d at 95. The final step in the
analysis arises under the analytical framework established by Ouellette—that is, where
federal common law previously governed the conduct (such as matters affecting interstate
water and air pollution) and is displaced by a legislative enactment (such as the Clean

52
B. The Clean Air Act, In Turn, Displaces Any Federal Common Law Claims that
the Local Governments May Have Where National Emissions Are Involved

Having determined that any claims the local governments may have would arise

under federal law, we next conclude that any federal common law claims would be

displaced by the Clean Air Act. We can make short work of this analysis given the

Supreme Court’s holding in AEP. See City of New York, 993 F.3d at 95 (“In the wake

of AEP, it is beyond cavil that the Clean Air Act displaced federal common law

nuisance suits seeking to abate domestic transboundary emissions of greenhouse

gases.”); see also Kivalina, 696 F.3d at 856 (explaining that the court “need not engage

in” the “complex issue and fact-specific analysis” of whether federal common law is

Water Act and the Clean Air Act), we consider whether Congress has authorized the
states to regulate the conduct through statutory enactments or the application of state
common law. 479 U.S. at 492. We determine that this framework, which the Second
Circuit applied to similar claims, is the correct one.

The dissent also criticizes our decision not to stay this case pending the United States
Supreme Court’s decision in Boulder, 2026 WL 490537, at *1. In Boulder, the United
States Supreme Court granted certiorari to determine two questions:

1. Whether federal law precludes state-law claims seeking relief for injuries
allegedly caused by the effects of intestate and international greenhouse-
gas emissions on the global climate.

2. Whether this Court has statutory and Article III jurisdiction to hear this
case.

Id. We decline to stay this case for two reasons. First, we believe that it could be useful
for the United States Supreme Court to have the benefit of a high court’s analysis that is
different from that expressed by our colleagues on the high courts of Colorado and Hawaii.
Second, given the Supreme Court’s decision to direct the parties to brief the second
question presented above, the Supreme Court may not even reach the merits.
53
displaced by the Clean Air Act “because we have direct Supreme Court guidance” and

citing to AEP).

We agree with the Second and Ninth Circuits that the Clean Air Act displaces not

only claims for abatement, but it similarly displaces the local governments’ common law

damages claims. City of New York, 993 F.3d. at 96; Kivalina, 696 F.3d at 857–58; see

also Middlesex County Sewerage Auth. v. Nat’l Sea Clammers Ass’n, 453 U.S. 1, 21–22

(1981) (holding that displacement of a federal common law injunction action necessarily

implies that a damages action brought for the same claim is also displaced). Whether the

local governments’ claims are styled as an action for injunctive relief against the

Defendants to stop them from producing fossil fuels, or as an action for a substantial

damages award that would alter their conduct vis-à-vis the production of fossil fuels, the

practical effect is the same.

Nor does the fact that the local governments are seeking to hold the Defendants

liable for emissions released by third parties—i.e., the worldwide consumers of fossil

fuel products who purchased and consumed more fuels, allegedly because of deceptive

marketing practices—alter our conclusion. “If an oil producer cannot be sued under the

federal common law for its own emissions, a fortiori it cannot be sued for someone

else’s.” City of New York, 993 F.3d at 97 (citation modified). Any claims that the local

governments could assert under federal common law are clearly displaced by the Clean

Air Act.

54
C. Applying the Ouellette Preemption Framework to the Local Governments’
Claims, Any State Law Claims Are Preempted

We also agree with the Second Circuit’s conclusion that, given the federalism

concerns undergirding the entire rationale of federal common law, 22 “state law does not
2 F

suddenly become presumptively competent to address issues that demand a unified

federal standard simply because Congress saw fit to displace a federal court-made

standard with a legislative one[.]” City of New York, 993 F.3d at 98. We recognize,

however, that Congress can grant states the authority to operate in an area of national

concern. But “resorting to state law on a question previously governed by federal

common law is permissible only to the extent authorized by federal statute.” Id. at 99

(citation modified) (quoting Milwaukee III, 731 F.2d at 411); see also Ouellette, 479

U.S. at 492. 23 In other words, where federal common law previously governed the
22F

conduct (such as matters affecting interstate water and air pollution) and is displaced by

22
See Milwaukee II, 451 U.S. at 313 n.7 (explaining that “if federal common law
exists, it is because state law cannot be used”); Boyle, 487 U.S. at 507 (noting that where
a federal statute displaces federal common law, it does so not “in a field which the States
have traditionally occupied”) (citation modified).
23
We agree with the Second Circuit that the case law applying preemption in the
context of state law claims that were once displaced by federal common law, which, in
turn, is displaced by Congress through a legislative enactment such as the CAA, “is
admittedly not a model of clarity[.]” City of New York, 993 F.3d at 98. As the Second
Circuit observed, “[a]lthough the Supreme Court in Ouellette appeared to rely, at least in
part, on the traditional preemption analysis under which courts should not lightly infer
preemption of state law claims,” the Ouellette Court also found support for its ultimate
conclusion—that the Clean Water Act had preempted state-law nuisance claims—by
looking to Milwaukee I, which held that, even in the absence of a federal statutory
scheme, “the control of interstate pollution is primarily a matter of federal law[.]” Id. at
103 n.11 (citation modified) (citing Ouellette, 479 U.S. at 492 (citing Milwaukee I, 407
U.S. at 107)).
55
a legislative enactment (such as the Clean Water Act and the Clean Air Act), we must

determine whether Congress has authorized the states to regulate the conduct through

statutory enactments or the application of state common law.

As discussed above, Ouellette provides the analytical framework that applies here.

The Court held that the Clean Water Act preempted Vermont’s nuisance suit under

Vermont law for harms experienced in Vermont but caused by New York-sourced

pollution. 479 U.S. at 483–84, 492. Relying on the Clean Water Act’s “comprehensive”

and “pervasive regulation” of water pollution, as well as “the fact that the control of

interstate pollution is primarily a matter of federal law,” the Court framed the inquiry as

whether the Clean Water Act “specifically preserved” the application of state law to water

pollution that originated from another state. Id. The Court answered no, holding that the

statue “contemplate[d] a much lesser role” for states seeking to regulate out-of-state

pollution, id. at 490, and precluded “applying the law of an affected State” to impose

liability on “an out-of-state source[,]” id. at 494.

Critically, the Court interpreted the Clean Water Act’s saving clause, 33 U.S.C.

§ 1370—which permits states to adopt and enforce stricter standards than required by the

Act—to permit liability under state law only if “pursuant to the law of the source State.”

Ouellette, 479 U.S. at 497. A contrary rule, the Court reasoned, would subject regulated

entities “to an indeterminate number of potential [state] regulations,” id. at 499,

“undermine the important goals of efficiency and predictability in the [EPA’s] permit

system,” id. at 496, and “undermine” the statute’s comprehensive “regulatory structure,”

id. at 497.

56
Applying the Supreme Court’s analytical framework to the local governments’

claims, we conclude that the Clean Air Act does not authorize the type of state law claims

that they assert. As discussed above, the Clean Air Act is a comprehensive federal law

that sets forth detailed source- and pollution-specific control programs for nationwide air

regulation. The Act grants the EPA authority to establish nationwide standards based

upon its expert judgment when the EPA determines that emissions from, for example,

stationary sources and new vehicles meet applicable statutory standards for regulation. 42

U.S.C. §§ 7411, 7521.

Although certain aspects of the Act embrace federal-state collaboration—such as

the attainment of NAAQS through state implementation plans—the plans must be

consistent with EPA regulations and submitted to the EPA for approval before they are

final. “[S]tates are not granted unfettered discretion to impose any environmental

regulations they choose[.]” City of New York, 993 F.3d at 81. Rather, the Act simply

“permit[s] each State to take the first cut at determining how best to achieve EPA

emissions standards within its domain.” AEP, 564 U.S. at 428 (emphasis added). The Act

carefully defines roles for states, including the state implementation plan process, in which

states implement EPA-promulgated standards for in-state sources.

The Clean Air Act specifically addresses the problem of “air pollution emitted in

one State, but causing harm in other States.” EPA v. EME Homer City Generation, L.P.,

572 U.S. 489, 495 (2014). Congress added the Good Neighbor Provision to “tackle [that]

problem” by requiring remedial action taken by the source state—because downwind

states “lack[ed] authority to control” out-of-state emissions. Id.; 42 U.S.C.

57
§ 7410(a)(2)(D)(i). Other provisions of the Clean Air Act afford affected states other

narrow avenues for voicing their cross-boundary pollution concerns to the EPA for

relevant pollutants. See, e.g., 42 U.S.C. § 7607(d)(5) (permitting “any person to submit

written comments, data, or documentary information[,]” and providing that “interested

persons” have “an opportunity” to orally present “data, views or arguments”); id. §

7475(a)(2) (noting that proposed permits for major emitting facilities must be subject to a

“public hearing”); id. § 7410(a)(1) (establishing that state implementation plans be

submitted “after reasonable notice and public hearings”). As this scheme makes plain,

each state is responsible for controlling air pollution within its borders—subject to EPA

oversight—and the Act contemplates no role for states reaching out and applying their law

in other states.

And although the Clean Air Act “provides multiple avenues for enforcement[,]”

AEP, 564 U.S. at 425—several of which contemplate state involvement—“only two could

even plausibly authorize the type of state-law claims pursued” by the local governments.

City of New York, 993 F.3d at 99. Those enforcement mechanisms set forth in two

provisions of the Act—42 U.S.C. §§ 7604(e) and 7416—are commonly and collectively

referred to by federal courts as the “saving clause.” Specifically, Section 7604(e) is a

citizen-suit saving clause, which states: “Nothing in this section shall restrict any right

which any person (or class of persons) may have under any statute or common law to seek

enforcement of any emission standard or limitation or to seek any other relief[.]” Section

7416 includes a states’ rights saving clause, which states: “Except as otherwise provided[,]

. . . nothing in this chapter shall preclude or deny the right of any State or political

58
subdivision thereof to adopt or enforce (1) any standard or limitation respecting emissions

of air pollutants or (2) any requirement respecting control or abatement of air pollution[,]”

except that the “State or political subdivision may not adopt or enforce any emission

standard or limitation” that is “less stringent than the standard or limitation” set by federal

law.

Several federal circuit courts of appeals have concluded that the saving clause

of the Clean Air Act is materially identical to the saving clause in the Clean Water Act

and have adopted the same interpretation that the Supreme Court adopted in

Ouellette—that the

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Source: Frix Law Library, https://www.frixlaw.com/law-library/cases/11281058. Public record. Not legal advice.