Amicus Curiae Brief — Virginia Duncan, et al., Petitioners v. Rob Bonta, Attorney General of California

No. 25-198

In the Supreme Court of the United States

__________

VIRGINIA DUNCAN, ET AL.,

Petitioners,

v.

ROB BONTA, ATTORNEY GENERAL OF CALIFORNIA,

Respondent.

____________________

ON PETITION FOR WRIT OF CERTIORARI TO THE

UNITED STATES COURT OF APPEALS FOR THE NINTH CIRCUIT

BRIEF OF MONTANA, IDAHO AND 25 OTHER

STATES AS AMICI CURIAE IN SUPPORT

OF PETITIONERS

__________

RAÚL R. LABRADOR

Attorney General

ALAN M. HURST

Solicitor General

SEAN M. CORKERY

Assistant Solicitor

General

OFFICE OF THE IDAHO

ATTORNEY GENERAL

700 W. Jefferson St

Suite 210

Boise, ID 83720

AUSTIN KNUDSEN

Attorney General

CHRISTIAN B. CORRIGAN*

Solicitor General

MONTANA DEPARTMENT OF

JUSTICE

215 N Sanders, 3rd Floor

Helena, MT 59620

406-444-2026

christian.corrigan@mt.gov

*Counsel of Record

Counsel for Amici Curiae

[Additional Signatories Listed On Signature Block]

i

TABLE OF CONTENTS

Page

Table of Authorities .....................................................ii

Interest of Amici Curiae .............................................. 1

Summary of the Argument ......................................... 2

Reasons for Granting the Writ.................................... 3

I. Lower courts in jurisdictions that tend to

restrict Second Amendment rights are defying

this Court’s precedents. ..................................... 3

A. Lower courts are misapplying the “common

use” test. ........................................................ 5

B. The so-called “nuanced approach” gives

lower courts an excuse to make loose

historical analogies. .................................... 10

II. The decision below badly erred. ...................... 14

A. Magazines are protected by the Second

Amendment. ................................................ 14

B. California bans magazines typically

possessed by law-abiding citizens for lawful

purposes. ..................................................... 17

C. The plus-ten magazine ban does not align

with this Nation’s tradition of firearm

regulation. ................................................... 22

Conclusion .................................................................. 26

ii

TABLE OF AUTHORITIES

Page(s)

Cases

Ass’n of N.J. Rifle & Pistol Clubs, Inc. v. Att’y Gen.

N.J.,

910 F.3d 106 (CA3 2018) ................................. 15, 16

Ass’n of N.J. Rifle & Pistol Clubs, Inc. v. Platkin,

742 F. Supp. 3d 421 (D.N.J. 2024) ........................ 10

Bevis v. City of Naperville,

85 F.4th 1175 (CA7 2023) ...................... 4, 7, 8, 9, 25

Bianchi v. Brown,

111 F.4th 438 (CA4 2024) ...................... 4, 6, 7, 8, 26

Caetano v. Massachusetts,

577 U.S. 411–21 (2016) .......................................... 18

Capen v. Campbell,

134 F.4th 660 (CA1 2025) .............................. 4, 9, 10

Del. State Sportsmen’s Ass’n, Inc. v. Del. Dep’t of

Safety & Homeland Sec.,

664 F. Supp. 3d 584 (D. Del. 2023) ....................... 10

District of Columbia v. Heller,

554 U.S. 570–77 (2008) ..... 5-10, 14, 17, 19, 20, 22, 24, 25

Duncan v. Becerra,

970 F.3d 1133 (CA9 2020) ........................... 6, 19, 24

Duncan v. Bonta,

19 F.4th 1087 (CA9 2021) ........................................ 6

iii

Ezell v. City of Chicago,

651 F.3d 684 (CA7 2011) ....................................... 15

Hanson v. District of Columbia,

671 F. Supp. 3d 1 (D.D.C. 2023) ............................ 16

Hanson v. Smith,

120 F.4th 223 (CADC 2024) .......... 6, 9-11, 15, 23-25

Harrel v. Raoul,

144 S. Ct. 2491 (2024) ....................................... 4, 12

Hartford v. Ferguson,

676 F. Supp. 3d 897 (W.D. Wash. 2023) ............... 10

Heller v. District of Columbia,

670 F.3d 1244 (CADC 2011) .................................. 19

Kolbe v. Hogan,

813 F.3d 160 (CA4 2016) ....................................... 15

Luis v. United States,

578 U.S. 5 (2016) ................................................... 14

Minneapolis Star & Trib. Co. v. Minnesota Comm’r of

Revenue,

460 U.S. 575 (1983) ......................................... 15, 16

N.Y. State Rifle & Pistol Ass’n v. City of New York,

590 U.S. 336 (2020) ............................................... 15

N.Y. State Rifle & Pistol Ass’n, Inc. v. Cuomo,

804 F.3d 242 (CA2 2015) ....................................... 19

Nat’l Ass’n for Gun Rights v. Lamont,

2025 U.S. App. LEXIS 21570 (CA2 Aug. 22, 2025)

................................................................................ 4, 10

iv

New York State Rifle & Pistol Ass’n, Inc. v. Bruen,

597 U.S. 1 (2022) ..... 2, 4-12, 14, 15, 17, 19, 20, 22, 23, 26

Ocean State Tactical, LLC v. Rhode Island,

95 F.4th 38 (CA1 2024) .................................. 4, 9, 10

Silvester v. Becerra,

138 S. Ct. 945 (2018) ............................................... 3

Snope v. Brown,

145 S. Ct. 1534 (2025) ................................... 3, 9, 10

State v. Gator’s Custom Guns, Inc.,

568 P.3d 278 (Wash. 2025) ...................................... 4

United States v. Duarte,

137 F.4th 743 (CA9 2025) ...................................... 12

United States v. Gonzalez,

792 F.3d 534 (CA5 2015) ................................. 15, 16

United States v. Rahimi,

602 U.S. 680 (2024) ........... 2, 6, 7, 12, 22, 23, 25, 26

Statutes

15 U.S.C. § 7901(b)(2) ............................................... 20

Other Authorities

J. Joel Alicea, Bruen Was Right,

174 U. Pa. L. Rev. (forthcoming 2025) ................. 5, 7

William Baude & Robert Leider, The General-Law

Right to Bear Arms,

99 Notre Dame L. Rev. 1467 (2024) ...................... 20

v

David B. Kopel, The History of Firearm Magazines

and Magazine Prohibitions,

78 Alb. L. Rev. 849 (2015) ......................... 18, 19, 24

1

INTEREST OF AMICI CURIAE

The States of Montana, Idaho, Alabama, Alaska,

Arkansas, Florida, Georgia, Iowa, Indiana, Kansas,

Kentucky,

Louisiana,

Mississippi,

Missouri,

Nebraska, New Hampshire, North Dakota, Ohio,

Oklahoma, South Carolina, South Dakota, Tennessee,

Texas, Utah, West Virginia, Wyoming, and the

Arizona Legislature submit this amicus brief to

safeguard citizens’ constitutional right to keep and

bear arms against unnecessary intrusions. That right

includes the right to possess and use essential

components of modern arms like plus-ten magazines.

Amici urge this Court to grant certiorari and reverse.*

* Under Rule 37.2, amici provided timely notice of their intention

to file this brief.

2

SUMMARY OF THE ARGUMENT

Though this case is now in its eighth year and on

its second trip to this Court, it should not have been

hard. The Ninth Circuit below agreed that about “half

of privately owned magazines hold more than ten

rounds,” “[m]ost pistols are manufactured with

magazines holding ten to seventeen rounds, and many

popular rifles are manufactured with magazines

holding twenty or thirty rounds.” App. 7. Time and

again, this Court has said that the Second

Amendment protects the right of citizens to bear arms

“that are unquestionably in common use today” for

lawful purposes. New York State Rifle & Pistol Ass’n,

Inc. v. Bruen, 597 U.S. 1, 47 (2022). Plus-ten

magazines are in common use today. So they are

protected by the Second Amendment.

Yet the Ninth Circuit joined several other courts in

rewriting the Second Amendment and this Court’s

precedents to allow hostile jurisdictions to continue

infringing on their citizens’ core constitutional right to

keep and bear arms. The Ninth Circuit claimed that

the Second Amendment does not apply at all because

California’s ban on the possession of plus-ten

magazines purportedly does not regulate arms—even

though the Second Amendment protects “armsbearing conduct,” including necessary incidents like

magazines. United States v. Rahimi, 602 U.S. 680, 691

(2024). The Ninth Circuit went on to botch its

alternative Second Amendment analysis, implausibly

concluding that plus-ten magazines are not in common

use and that irrelevant regulations like gunpowder

storage rules are historical analogues for California’s

ban.

3

This obvious error from the Nation’s largest circuit

on a core issue of constitutional law warrants this

Court’s review. More fundamentally, it is time for this

Court to address the repeated defiance of this Court’s

teachings, particularly in the circuits containing most

of the jurisdictions that have repeatedly infringed on

citizens’ Second Amendment rights. The evident

errors below and in similar cases manifest a deep

hostility to both the Second Amendment itself and this

Court’s precedents. Only this Court’s review can

correct these persistent misapplications, which

deprive citizens of their fundamental rights, their

property, and their ability to defend themselves. The

Court should grant certiorari and reverse.

REASONS FOR GRANTING THE WRIT

I. Lower courts in jurisdictions that tend to

restrict Second Amendment rights are

defying this Court’s precedents.

The Ninth Circuit’s “dismissive” view of the Second

Amendment is no anomaly—it “is emblematic of a

larger trend.” Silvester v. Becerra, 138 S. Ct. 945, 950

(2018) (Thomas, J., dissenting from denial of

certiorari). “[L]ower courts in the jurisdictions that”

most often restrict Second Amendment rights “appear

bent on distorting this Court’s Second Amendment

precedents.” Snope v. Brown, 145 S. Ct. 1534, 1538

(2025) (Thomas, J., dissenting from denial of

certiorari). Whatever the mechanism—sometimes

distorting the term “arms,” other times a convoluted

understanding of the “common use” test, still other

times faulty historical analogies—the effect of these

lower court decisions is clear: “to trammel the

constitutional liberties” of citizens, especially in

4

jurisdictions already hostile to Second Amendment

rights. Bianchi v. Brown, 111 F.4th 438, 483 (CA4

2024) (Richardson, J., dissenting). To address this

effect of far-reaching defiance of this Court’s

precedents, certiorari is needed.

Widespread

infringement

of

the

Second

Amendment is not a hypothetical concern but a

reality. Several courts have already upheld outright

bans on “America’s most common civilian rifle,” the

AR-15. Harrel v. Raoul, 144 S. Ct. 2491, 2493 (2024)

(Thomas, J., statement respecting the denial of

certiorari); see, e.g., Nat’l Ass’n for Gun Rights v.

Lamont, Nos. 23-1162, 23-1344, 2025 U.S. App. LEXIS

21570, at *66 (CA2 Aug. 22, 2025); Capen v. Campbell,

134 F.4th 660, 677 (CA1 2025); Bevis v. City of

Naperville, 85 F.4th 1175, 1182 (CA7 2023). Plus-ten

magazines have faced similar bans, which have been

upheld by the Ninth Circuit below and other courts.

See, e.g., State v. Gator’s Custom Guns, Inc., 568 P.3d

278, 281 (Wash. 2025); Lamont, 2025 U.S. App. LEXIS

21570, at *15, *66; Ocean State Tactical, LLC v. Rhode

Island, 95 F.4th 38, 52 (CA1 2024).

Judicial defiance seemed to drive these outcomes,

not a careful application of the Bruen framework. Two

specific forms of judicial defiance stand out in the

lower courts’ decisions on arms bans: (A) a convoluted

understanding of the “common use” test; and (B)

application of the purportedly separate “nuanced

approach” to historical analogues.

5

A. Lower courts are

“common use” test.

misapplying

the

Begin with a brief explanation of the Bruen

framework of “common use.” In Bruen, this Court

described two steps “for applying the Second

Amendment.” 597 U.S. at 24. The first step explains

that “[w]hen the Second Amendment’s plain text

covers an individual’s conduct, the Constitution

presumptively protects that conduct.” Ibid. Step one is

a purely “‘textual analysis’ focused on the ‘normal and

ordinary’ meaning of the Second Amendment’s

language.” Id. at 20 (cleaned up) (quoting District of

Columbia v. Heller, 554 U.S. 570, 576–77, 578 (2008));

see J. Joel Alicea, Bruen Was Right, 174 U. Pa. L. Rev.

(forthcoming 2025) (manuscript at 9) (“[T]he first step

focuses on the original semantic meaning of the text.”).

So to succeed at step one, a citizen must show that the

object he seeks to possess is an “Arm” according to the

“normal and ordinary” meaning of the Second

Amendment. Bruen, 597 U.S. at 20.

The original “meaning [of ‘Arms’] is no different

from the meaning today.” Heller, 554 U.S. at 581.

“Arms” are “weapons of offence, or armour of defence.”

Ibid. (cleaned up). Thus, at step one, “it does not

matter whether the object in question is a handgun or

a machine gun.” Alicea, supra, at 15 (cleaned up). But

it would matter if the relevant object were a banana.

A banana receives no presumptive protection under

the Second Amendment, but a firearm does.

Bruen step two requires “[t]he government” to

“justify its regulation by demonstrating that it is

consistent with the Nation’s historical tradition of

firearm regulation.” 597 U.S. at 24. Courts must use

6

“analogical reasoning” to assess whether the modern

regulation is “relevantly similar” to historical

regulations. Id. at 28–29. “Why and how the

regulation burdens the right are central to this

inquiry.” Rahimi, 602 U.S. at 692. “The law must

comport with the principles underlying the Second

Amendment, but it need not be a ‘dead ringer’ or a

‘historical twin.’” Ibid. (quoting Bruen, 597 U.S. at 30).

The “common use” test, in turn, is the test for

discerning whether an arm may be regulated

according to the “tradition of prohibiting the carrying

of ‘dangerous and unusual weapons.’” Heller, 554 U.S.

at 627. An arm is not “dangerous and unusual” if it is

“typically possessed by law-abiding citizens for lawful

purposes.” Id. at 625, 627. Put another way, if an arm

is “in common use today” by “American society” for a

“lawful purpose,” then it cannot be banned. Id. at 628;

see Bruen, 597 U.S. at 47; see also Hanson v. Smith,

120 F.4th 223, 271 (CADC 2024) (Walker, J.,

dissenting) (“Heller and its progeny . . . have already

held that the government cannot ban an arm in

common use for lawful purposes.”).

The next question is how common an arm must be

to receive protection. “Commonality is determined

largely by statistics. But a pure statistical inquiry may

hide as much as it reveals,” for “protected arms may

not be numerically common by virtue of an

unchallenged, unconstitutional regulation.” Duncan v.

Becerra, 970 F.3d 1133, 1147 (CA9 2020) (App. 584),

rev’d en banc sub. nom., Duncan v. Bonta, 19 F.4th

1087 (CA9 2021). Courts should “look[] to the usage of

the American people to determine which weapons they

deem most suitable for lawful purposes.” Bianchi, 111

7

F.4th at 522 (Richardson, J., dissenting); see Heller,

554 U.S. at 629 (“It is enough to note . . . that the

American people have considered the handgun to be

the quintessential self-defense weapon.”).

The “common use” test is best understood as part

of Bruen step two because it is a limitation on the

Second Amendment’s scope “supported by the

historical tradition” of regulating “dangerous and

unusual weapons.” Heller, 554 U.S. at 627; see

Bianchi, 111 F.4th at 502 (Richardson, J., dissenting)

(“the ‘common use’ inquiry best fits at Bruen’s second

step”); see also Alicea, supra, at 13. The “common use”

test is not part of Bruen’s plain-text analysis at step

one—whether an arm is “in common use” does not

determine whether it is actually an arm. See Bevis, 85

F.4th at 1209 (Brennan, J., dissenting) (“The nature of

an object does not change based on its popularity, but

the regulation of that object can.”).

“Rahimi confirms this” understanding. Bianchi,

111 F.4th at 502 n.29 (Richardson, J., dissenting).

This Court considered Mr. Rahimi to be part of the

“the people” at step one—despite his violent history

that ultimately justified his temporary dispossession

at step two—because “the term unambiguously refers

to all members of the political community.” Rahimi,

602 U.S. at 773 (Thomas, J., dissenting) (internal

quotation marks omitted). “[J]ust as the term ‘the

people’ includes but is not limited to ordinary, lawabiding, adult citizens, the term ‘Arms’ includes but is

not limited to arms in common use.” Bianchi, 111

F.4th at 502 n.29 (Richardson, J., dissenting). And it

matters which step the “common use” test occurs at

8

because the burden of proof shifts from the litigant to

the government at step two. See Bruen, 597 U.S. at 24.

With those principles in mind, turn to the lower

courts’ treatment of the “common use” test.

Considering Maryland’s ban on AR-15s, the Fourth

Circuit chastised the test as a “trivial counting

exercise” and an “ill-conceived popularity test.”

Bianchi, 111 F.4th at 460. Then, the court misapplied

an incorrect version of the test at the wrong step to

conclude that AR-15s are not “Arms” presumptively

protected by the Second Amendment—putting an AR15 and a banana on equal footing. See id. at 452–53.

The court reasoned that an individual must first

demonstrate that a weapon is not “dangerous and

unusual” for the weapon to be considered an “Arm”

presumptively protected by the Second Amendment.

See id. at 450–53. Rather than look to common usage

among citizens, the Fourth Circuit concocted an

interest balancing test that asks whether an arm is

“excessively dangerous [and] not reasonably related or

proportional to the end of self-defense.” Id. at 450, 452.

In so doing, the court “balance[d] away Second

Amendment freedoms” and “decide[d] [for itself] which

weapons are most suitable” for Americans. Id. at 522,

531 (Richardson, J., dissenting).

Likewise, considering Illinois’s ban on AR-15s, the

Seventh Circuit warped the “common use” analysis to

conclude that AR-15s are not “Arms.” See Bevis, 85

F.4th at 1195. The court misinterpreted the “common

use” test to mean that the government may ban

weapons that “may be reserved for military use,”

simply because Heller mentioned that M-16s could be

banned. Id. at 1194. And the court placed the burden

9

on the plaintiff to make a showing of “common use” at

step one. See id. So rather than focus on the “normal

and ordinary meaning” of “Arm” historically, the court

engaged in a “matching exercise between” “the

characteristics of the” AR-15 and the M-16. Bruen, 597

U.S. at 20 (internal quotation marks omitted); see

Bevis, 85 F.4th at 1221–22 (Brennan, J., dissenting).

And, in the Seventh Circuit’s eyes, “the AR-15 is

almost the same gun as the M16 machinegun” used by

the military, so the AR-15 is not an arm and can be

banned. Bevis, 85 F.4th at 1195. But to the extent the

M-16 “‘may be banned,’” that is “not because of its

military use but because of the ‘historical tradition of

prohibiting the carrying of dangerous and unusual

weapons.’” Hanson, 120 F.4th at 233 (quoting Heller,

554 U.S. at 627); see Snope, 145 S. Ct. at 1534

(Kavanaugh, J., statement respecting the denial of

certiorari).

Even courts that address the common use test at

the right step still confuse the analysis. In a case

involving Rhode Island’s ban on plus-ten magazines,

the First Circuit declared that this Court has not

“intimated that a weapon’s prevalence in society (as

opposed to, say, the degree of harm it causes) is the

sole measure of whether it is ‘unusual.’” Ocean State

Tactical, 95 F.4th at 50–51; see also Capen, 134 F.4th

at 669–71 (upholding Massachusetts’s ban of AR-15s

based largely on this reasoning). And the First Circuit

said that courts should look beyond the “ownership

rate of the weapons at issue” to the weapon’s

“usefulness for self-defense.” Ocean State Tactical, 95

F.4th at 51. To the contrary, Heller concluded that the

District of Columbia could not “totally ban[] handgun

10

possession in the home” because handguns were

“overwhelmingly chosen by American society for

[lawful purposes].” Heller, 554 U.S. at 628 (emphasis

added). “Our Constitution allows the American

people—not the government—to decide which

weapons are useful for self-defense.” Snope, 145 S. Ct.

at 1537 (Thomas, J., dissenting from denial of

certiorari).

These consistent misapplications of the common

use test, especially in jurisdictions most likely to

restrict Second Amendment rights, require this

Court’s attention.

B. The so-called “nuanced approach” gives

lower courts an excuse to make loose

historical analogies.

Lower courts overseeing hostile jurisdictions—

including the Ninth Circuit below—have also erred by

distorting Bruen to apply a “nuanced approach” that

effectively reduces the government’s burden at step

two. See, e.g., App. 30–31; Lamont, 2025 U.S. App.

LEXIS 21570, at *27; Hanson, 120 F.4th at 240–41;

Capen, 134 F.4th at 668; Ocean State Tactical, 95

F.4th at 44; Del. State Sportsmen’s Ass’n, Inc. v. Del.

Dep’t of Safety & Homeland Sec., 664 F. Supp. 3d 584,

598 (D. Del. 2023), aff’d, 108 F.4th 194 (CA3 2024);

Ass’n of N.J. Rifle & Pistol Clubs, Inc. v. Platkin, 742

F. Supp. 3d 421, 449 (D.N.J. 2024); Hartford v.

Ferguson, 676 F. Supp. 3d 897, 907 (W.D. Wash. 2023).

Bruen explained that “the historical analogies here

and in Heller are relatively simple to draw,” while

noting that “other cases implicating unprecedented

societal concerns or dramatic technological changes

11

may require a more nuanced approach.” 597 U.S. at

27. Several lower courts have taken this passing

remark far beyond its limited scope. These courts

apply a different version of Bruen step two in “cases

implicating unprecedented societal concerns or

dramatic technological changes.” Hanson, 120 F.4th at

241. For instance, under the D.C. Circuit’s variety,

“the government may demonstrate a constitutionally

adequate”—meaning, loose—”historical analogue for a

regulation or ban of an arm implicating either”

societal concerns or technological changes. Ibid. In a

case involving the District of Columbia’s plus-ten

magazine ban, the D.C. Circuit held that these

magazines “implicate unprecedented societal concerns

and dramatic technological changes,” so “the lack of a

‘precise match’ does not” matter. Id. at 242.

This “nuanced approach” licenses courts to

“disregard our historical tradition of firearm

regulation whenever a modern regulation seeks to

address modern problems or technology.” App. 112–13

(Bumatay, J., dissenting). The “single stray line of

dicta from Bruen” mentioning a “nuanced approach”

did not create a different version of the Bruen test or

erase the “common use” test. Hanson, 120 F.4th at 275

(Walker, J., dissenting). Instead, it “was an

unremarkable observation that making comparisons

to proper historical analogies might be challenging at

times.” App. 113 (Bumatay, J., dissenting). Under

Bruen, “analogical reasoning requires” “that the

government identify a well-established and

representative historical analogue.” 597 U.S. at 30. To

read Bruen as creating an alternate, historically lax

test would miss the core point of the decision: courts

12

must “assess whether modern firearms regulations

are consistent with the Second Amendment’s text and

historical understanding.” Bruen, 597 U.S. at 26; see,

e.g., Rahimi, 602 U.S. at 708 (Gorsuch, J., concurring);

id. at 717–18 (Kavanaugh, J., concurring); id. at 737–

39 (Barrett, J., concurring); id. at 750–51 (Thomas, J.,

dissenting).

*

*

*

Lower courts are not faithfully applying this

Court’s Second Amendment precedents. Outcomes

like upholding blanket bans on “America’s most

common civilian rifle” did not result from analytical

disagreements about historical gun regulation

analogues. Harrel, 144 S. Ct. at 2493 (statement of

Thomas, J.). Instead, too many lower courts use

“‘cherrypicked language’ that is ‘mis- and over-applied

from the Court’s prior precedents’ to uphold any

firearms regulation that comes before [them].” United

States v. Duarte, 137 F.4th 743, 782 (CA9 2025) (en

banc) (VanDyke, J., concurring). And too many of

those decisions come from circuits whose jurisdictions

are most likely to restrict their citizens’ Second

Amendment rights:

13

See U.S. Concealed Carry Ass’n, Which States Have

Assault

Weapons

Bans?

(June

30,

2025),

https://perma.cc/RQ5Y-WDGU; U.S. Concealed Carry

Ass’n, Gun Magazine Capacity Laws by State (Sept.

25, 2023), https://perma.cc/5JTS-DV86.

14

This combination of legislative and judicial

defiance to the Court’s precedents serves as a double

whammy to the constitutional rights of law-abiding

Americans. It is again time for the Court to step in.

II. The decision below badly erred.

The Ninth Circuit below repeated many of the

errors discussed above, perpetuating its underprotection of Second Amendment rights. First, it

contorted the meaning of “arms” to hold that

magazines carrying ammunition necessary to a gun’s

operation are unprotected by the Second Amendment.

Second, it held that plus-ten magazines are not in

common use—despite their exceedingly widespread

private ownership—because they may not often be

used directly to fire in self-defense. Third, it invoked

inapt historical regulations, like gunpowder storage

laws, to justify the heavy burden placed by California’s

law on Second Amendment rights. Each of these

moves was egregiously wrong.

A. Magazines are protected by the Second

Amendment.

The Second Amendment preserves the right of the

people to keep and bear “arms,” which “covers modern

instruments that facilitate armed self-defense.”

Bruen, 597 U.S. at 28. Its protections extend, “prima

facie, to all instruments that constitute bearable arms,

even those that were not in existence at the time of the

founding.” Heller, 554 U.S. at 582.

“Constitutional rights,” including those within the

Second Amendment, “implicitly protect those closely

related acts necessary to their exercise.” Luis v.

United States, 578 U.S. 5, 26 (2016) (Thomas, J.,

15

concurring). For instance, the Second Amendment

includes “necessary concomitant[s]” like “the right to

take a gun outside the home for certain purposes.”

N.Y. State Rifle & Pistol Ass’n v. City of New York, 590

U.S. 336, 364 (2020) (Alito, J., dissenting). And it

encompasses integral parts of firearms like bullets

and magazines. Just as the First Amendment

prohibits, for instance, indirect regulation via

differential taxes on paper and ink, Minneapolis Star

& Trib. Co. v. Minnesota Comm’r of Revenue, 460 U.S.

575, 593 (1983), the Second Amendment prohibits

regulations that burden the right to keep and bear

arms. See Ezell v. City of Chicago, 651 F.3d 684, 704

(CA7 2011).

Several courts, both pre- and post-Bruen, have

recognized that magazines are within the Second

Amendment’s protections. See Ass’n of N.J. Rifle &

Pistol Clubs, Inc. v. Att’y Gen. N.J., 910 F.3d 106, 116

(CA3 2018); Kolbe v. Hogan, 813 F.3d 160, 175 (CA4

2016). Even the D.C. Circuit, which upheld a plus-ten

magazine ban, concluded that magazines are

protected. Hanson, 120 F.4th at 232. And rightly so.

“A magazine is necessary to make meaningful an

individual’s [Second Amendment] right.” Ibid.

(cleaned up).

As Judge Bumatay explained below, “If magazines

and other components weren’t included, the Second

Amendment would be a shallow right—easily

infringed by basic indirect regulation.” App. 84

(dissenting op.). Indeed, magazines are inherently tied

to the arm itself. “The problem of limited ammunition

capacity has plagued rifles since their invention

centuries ago.” United States v. Gonzalez, 792 F.3d

16

534, 536 (CA5 2015). “The earliest rifles fired a single

shot, leaving the user vulnerable during reloading.”

Ibid. “Numerous inventions have sought to eliminate

this problem,” but “none has proved as effective as the

magazine.” Ibid.

Below, the Ninth Circuit majority claimed that

plus-ten “magazine[s] [are] no different than other

items that hold additional ammunition, such as

cartridge boxes and belts that hold bullets.” App. 21.

That’s true in the same sense that a motor vehicle’s

gas tank holds additional fuel. It’s theoretically

possible to operate a gas-powered vehicle without a

gas tank, but that would severely limit its

functionality and utility. See Ass’n of N.J. Rifle &

Pistol Clubs, 910 F.3d at 116 (“[M]agazines feed

ammunition into certain guns, and ammunition is

necessary for such a gun to function as intended.”).

Likewise, it’s theoretically possible to operate a

newspaper by paying higher taxes on ink and paper,

but that did not free those taxes from First

Amendment scrutiny. See Minneapolis Star, 460 U.S.

at 583.

As the district court in Hanson observed,

classifying magazines as mere “accoutrements” would

allow states “to ban all magazines . . . because a

firearm technically does not require any magazine to

operate; one could simply fire the single bullet in the

firearm’s chamber.” Hanson v. District of Columbia,

671 F. Supp. 3d 1, 10 (D.D.C. 2023). And if magazines

are not protected by the Second Amendment, “States

could make an easy end-run around the Second

Amendment by simply banning firearm components.”

App. 282 (Bumatay, J., dissenting). The Ninth

17

Circuit’s logic would likewise permit states to limit the

capacity of revolvers or other firearms without

detachable magazines.

Because magazines are integral to “arms,” they are

protected by the Second Amendment, and California

bears the burden of proof under Bruen’s history and

tradition framework. See Bruen, 597 U.S. at 17.

B. California bans magazines typically

possessed by law-abiding citizens for

lawful purposes.

The Ninth Circuit also botched the “common use”

analysis. The Second Amendment protects arms

“typically possessed by law-abiding citizens for lawful

purposes.” Heller, 554 U.S. at 625 (cleaned up). This

“common use” test accounts for the historical

“tradition of prohibiting the carrying of ‘dangerous

and unusual weapons.’” Id. at 627. Arms “in common

use today” are not “dangerous and unusual.” Bruen,

597 U.S. at 47 (internal quotation marks omitted).

So are plus-ten magazines typically possessed by

law-abiding citizens for lawful purposes? The answer

is unequivocally yes—so they cannot be considered

dangerous and unusual. Those magazines are

commonly used for self-defense, hunting, and sporting

purposes. California’s restrictions, like similar

restrictions in other States, burden the rights of

millions of law-abiding citizens to keep and bear

magazines (or “arms”) that have long been considered

appropriate for self-defense.

The district court properly concluded that “[t]here

is no American tradition of limiting ammunition

capacity and the 10-round limit has no historical

18

pedigree.” App. 307. “It is indisputable in the modern

United States that magazines of up to thirty rounds

for rifles and up to twenty rounds for handguns are

standard equipment for many popular firearms.”

David B. Kopel, The History of Firearm Magazines

and Magazine Prohibitions, 78 Alb. L. Rev. 849, 874

(2015). And they are legal in “at least 38 States and

under Federal law.” App. 74–75 (Bumatay, J.,

dissenting). In one comprehensive study, 48% of

respondents confirmed that they owned plus-ten

magazines. App. 313. Estimates vary, but another

study found that Americans own 542 million plus-ten

magazines. Ibid. So they’re not just common, they’re

ubiquitous in common guns, like the Glock 17—one of

the most popular firearms on the market—that comes

with a standard 17-round magazine. App. 587.

Of course, an arm need not number in the millions

to be in common use. This Court held that stun guns

are in common use even though only a few hundred

thousand citizens own such arms. Caetano v.

Massachusetts, 577 U.S. 411, 420–21 (2016) (Alito, J.,

concurring). “While less popular than handguns, stun

guns are widely owned and accepted as a legitimate

means of self-defense across the country.” Id. at 420.

Thus, the common use threshold is relatively low. And

if a few hundred thousand stun guns reach that

threshold, then millions of plus-ten magazines far

surpass it.

The evidence before the district court was neither

surprising nor unique. The district court concluded

that plus-ten magazines are “commonly-owned by

law-abiding citizens” and are not “dangerous and

unusual.” App. 346. And courts across the country

19

have recognized the widespread use of these

magazines by law-abiding citizens. See N.Y. State

Rifle & Pistol Ass’n, Inc. v. Cuomo, 804 F.3d 242, 255

(CA2 2015) (agreeing that the “large-capacity

magazines at issue are ‘in common use’”); Heller v.

District of Columbia, 670 F.3d 1244, 1261 (CADC

2011) (noting that the record showed that “magazines

holding more than ten rounds are indeed in ‘common

use”‘).

Moreover, there’s a longstanding history and

tradition of law-abiding Americans owning and using

these magazines for self-defense. A prior panel below

aptly explained that “[f]irearms or magazines holding

more than ten rounds have been in existence—and

owned by American citizens—for centuries. Firearms

with greater than ten round capacities existed even

before our nation’s founding, and the common use of

[plus-ten magazines] for self-defense is apparent in

our shared national history.” Duncan, 970 F.3d at

1147 (App. 585); see also App. 284 (Bumatay, J.,

dissenting) (“In terms of large-scale commercial

success, rifle magazines of more than ten rounds had

become popular by the time the Fourteenth

Amendment was being ratified.” (quoting Kopel,

supra, at 851)).

The majority below concluded that plus-ten

magazines are “rarely . . . used in self-defense” and

thus may be banned. App. 53. But that’s wrong in

several respects.

First, though self-defense is a core component of

the Second Amendment, Bruen, 597 U.S. at 29, the

constitutional right to keep and bear arms is not

limited to self-defense. The right extends to other

20

“lawful purpose[s]” too, like community defense,

hunting, and sporting. Heller, 554 U.S. at 624; see,

e.g., id. at 599; 15 U.S.C. § 7901(b)(2); William Baude

& Robert Leider, The General-Law Right to Bear

Arms, 99 Notre Dame L. Rev. 1467, 1498–1502 (2024).

And this Court in Bruen reiterated that the Second

Amendment protects arms “in common use,” not

merely those in common use for self-defense. Bruen,

597 U.S. at 21.

Second, the reasoning below is inconsistent with

Heller. Heller “consider[ed] whether a District of

Columbia prohibition on the possession of usable

handguns in the home violates the Second

Amendment.” 554 U.S. at 573. “Actual firing of a

handgun in the District was irrelevant.” App. 332.

Rather, “[c]onstitutional protection is afforded to

weapons ‘typically possessed by law-abiding citizens

for lawful purposes,’ focusing on typicality and

possession rather than frequency of firing.” Ibid.

(quoting Heller, 554 U.S. at 625).

Third, even if actual firing mattered, the Ninth

Circuit would still be wrong. These magazines

facilitate armed self-defense. The district court cited a

comprehensive study showing that American gun

owners use firearms in self-defense roughly 1.7 million

times every year. App. 313 (citing William English,

2021 National Firearms Survey: Updated Analysis

Including Types of Firearms Owned 35 (Geo.

McDonough Sch. of Bus. Rsch. Paper No. 4109494,

2022)). Another study from the Centers for Disease

Control puts that number as high as 3 million. App.

313–14 (citing Inst. of Med. & Nat’l Rsch. Council,

Priorities for Research to Reduce the Threat of

21

Firearm-Related Violence 15 (The Nat’l Acads. Press

ed., 2013)).

And that’s only part of the equation. “[I]t is

unnecessary to look at how often a law-abiding citizen

fired a firearm more than ten times to fend off an

attacker for our inquiry,” for “it would be troubling if

our constitutional rights hung on such thin evidence.”

App. 286 (Bumatay, J., dissenting). As discussed,

nearly half of gun owners possess plus-ten magazines.

And there are likely hundreds of millions of those

magazines in circulation—many used in popular

firearms such as the Glock 17. So when someone uses

a firearm in self-defense, whether to fend off an

intruder in the middle of the night or a grizzly bear in

the middle of nowhere, there’s a good chance that

person is “using” a plus-ten magazine. The same is

true when individuals use firearms as a deterrent in

self-defense situations without firing a shot. The “use”

of the firearm isn’t limited to firing the weapon. The

district court rightly analogized this to wearing a

seatbelt in case of collision or using a reserve canopy

on a parachute. App. 335. Firing a weapon in selfdefense—one time or fifteen times—is always a worstcase scenario. Fortunately, the Second Amendment

protects the right of Americans to adequately prepare

themselves for those contingencies.

C. The plus-ten magazine ban does not align

with this Nation’s tradition of firearm

regulation.

California’s plus-ten magazine ban is not

analogous to any of the historical regulations invoked

by the Ninth Circuit. “[W]hen the Government

regulates arms-bearing conduct, as when the

22

Government regulates other constitutional rights, it

bears the burden to ‘justify its regulation.’” Rahimi,

602 U.S. at 691. To justify its plus-ten magazine ban,

California must demonstrate that “its regulation” “is

consistent with the Nation’s historical tradition of

firearm regulation”—”[o]nly then may a court

conclude that” possessing these magazines “falls

outside the Second Amendment’s ‘unqualified

command.’” Bruen, 597 U.S. at 24.

Courts must follow the course charted by Heller,

Bruen, and Rahimi to determine whether modern

firearm regulations are consistent with the Second

Amendment’s text and historical understanding. That

analysis requires courts to “ascertain whether the new

law is ‘relevantly similar’ to laws that our tradition is

understood to permit.” Rahimi, 602 U.S. at 692. And

relevant similarity exists if “the government

identif[ies] a well-established and representative

historical analogue.” Bruen, 597 U.S. at 30. “Why and

how the regulation burdens the right are central to

[the analogical] inquiry.” Rahimi, 602 U.S. at 692.

Even though California’s obligation to respect

citizens’ right to keep and bear arms flows from the

Fourteenth Amendment, not the Second, the rights

listed in the Bill of Rights and incorporated against

the States after the Fourteenth Amendment’s

adoption “have the same scope as against the Federal

Government.” Bruen, 597 U.S. at 37. And the scope of

that right is generally “pegged to the public

understanding of the right when the Bill of Rights was

adopted in 1791.” Ibid. (collecting cases).

The Ninth Circuit majority’s “historical tradition”

analysis is flawed from the get-go. It made the same

23

mistake that other courts have in reasoning that “a

more nuanced approach applies to cases” “implicating

unprecedented societal concerns or dramatic

technological changes.” App. 30–31 (quoting Bruen,

597 U.S. at 27). “Those cases,” the Ninth Circuit

reasoned, “warrant an even more flexible approach

than the Court applied in Rahimi.” App. 31. And the

“nuanced approach [was] appropriate here” because

“mass shootings” are a recent “societal concern,” and

plus-ten

magazines

“represent

a

dramatic

technological change from the weapons at the

Founding.” App. 31–32.

But again, the “nuanced approach” is not a

separate test. See Hanson, 120 F.4th at 275 (Walker,

J., dissenting). There is only “one approach: the

Second

Amendment’s

text

and

historical

understanding always control.” App. 113 (Bumatay,

J., dissenting).

The Ninth Circuit relied on three historical

regulatory regimes: laws regulating the storage of

gunpowder, laws regulating trap guns, and laws

restricting “weapons after their use by criminals

exposed an especially dangerous use of the weapon.”

App. 34–39. But these historical comparisons are

incomplete because firearms with greater than tenround capacity have existed since 1580 and were wellknown to the Founders. See Duncan, 970 F.3d at 1147,

1149 (App. 585). In other words, the Ninth Circuit

evaluated the modern regulation of apples by

analogizing to the historical regulation of oranges. In

some cases, that could be necessary. But we have a

better historical analogue—the actual regulation of

apples (or lack thereof).

24

A prior Ninth Circuit panel detailed the history of

these firearms. See generally id. at 1147–49 (App.

585–88). Importantly, “[a]fter the American

Revolution . . . new firearm designs proliferated

throughout the states and few restrictions were

enacted on firing capacities.” Id. at 1147 (App. 585).

The Lewis and Clark Expedition carried the

Girandoni air rifle in 1804, which had a 22-round

capacity. Ibid. In 1867, Winchester introduced its

famous Model 66 lever-action rifle able to carry 17

rounds—just like the modern Glock 17. Id. at 1148

(App. 586); see also Kopel, supra, at 851.

Setting this overlooked history aside, the Ninth

Circuit’s proposed analogies still fail. Colonial-era

regulations on gunpowder storage are inapplicable to

magazine-capacity restrictions. “The suggestion that

the[se laws] limited the Second Amendment right to

keep and bear arms is silly.” Hanson, 120 F.4th at 235.

First, the burden on law-abiding citizens is

asymmetric, for “those fire-safety laws” did “not

remotely burden the right of self-defense as much as

an absolute ban on handguns.” Heller, 554 U.S. at 632.

“While California’s magazine ban prohibits using the

most popular magazine for self-defense, the

gunpowder laws had zero effect on self-defense.” App.

110 (Bumatay, J., dissenting). Second, these laws

served a different purpose. “The ‘why’ of the

gunpowder regulations was to stop fires resulting

from the combustion of stored flammable materials.”

Bevis, 85 F.4th at 1217 (Brennan, J., dissenting).

That’s different than “California’s purpose” here:

“reduc[ing] intentional gun violence.” App. 110

(Bumatay, J., dissenting).

25

The Ninth Circuit’s analogy to trap gun

regulations also fails. Trap guns involved “the rigging

of a firearm to discharge when a person unwittingly

trips a string or wire.” App. 35. But trap gun

regulations and California’s magazine ban do not

share “similar reasons” for their enactment. Rahimi,

602 U.S. at 692. Setting trap guns is inherently

unlawful—it amounts to “tortious activity that lies

outside the realm of lawful self-defense.” Hanson, 120

F.4th at 236. By contrast, California’s magazine ban

targets actions—owning and using plus-ten

magazines—that merely have the potential for

unlawful abuse. And the “how” is different because

laws against trap guns only banned “the setting of the

device,” unlike California’s outright ban on plus-ten

magazines. App. 109 (Bumatay, J., dissenting).

Neither does the Ninth Circuit’s analogy to anticarry laws stand up. The court discerned a tradition of

banning “especially dangerous uses of weapons” based

on historical regulations restricting the carry of

weapons like “Bowie knives,” “slungshots,” and

concealable “percussion-cap pistols.” App. 34–39. But

that “evade[s]” and “recharacteriz[es]” “Heller’s clear

ruling” that dangerous and unusual arms may be

prohibited while those in common use may not. App.

98 (Bumatay, J., dissenting).

Even if the Ninth Circuit correctly identified a

tradition of regulating “especially dangerous uses of

weapons,” it still would not be “relevantly similar” to

California’s magazine ban. The “how” is different

because anti-carry laws restrict the specific “manner

of carrying,” while the magazine ban prohibits

possession altogether. Bianchi, 111 F.4th at 510

26

(Richardson, J., dissenting). And the “why” fares no

better because the court identified an overly broad

historical principle. See Rahimi, 602 U.S. at 740

(Barrett, J., concurring) (“[A] court must be careful not

to read a principle at such a high level of generality

that it waters down the right.”). Under “the majority’s

permissive ‘especially dangerous’ level of generality”

“there always will be a matching ‘why’ because [of] the

inherently dangerous nature of firearms.” App. 139–

40 (VanDyke, J., dissenting).

The Ninth Circuit’s overly broad analogizing, along

with its other errors, gives California and other States

within that circuit “a regulatory blank check” to chip

away at the Second Amendment rights of millions of

Americans. Bruen, 597 U.S. at 30.

CONCLUSION

The Court should grant the petition and reverse.

Respectfully submitted,

SEPTEMBER 18, 2025

RAÚL R. LABRADOR

Attorney General

ALAN M. HURST

Solicitor General

SEAN M. CORKERY

Assistant Solicitor

General

OFFICE OF THE IDAHO

ATTORNEY GENERAL

700 W. Jefferson St

Suite 210

Boise, ID 83720

AUSTIN KNUDSEN

Attorney General

CHRISTIAN B. CORRIGAN*

Solicitor General

MONTANA DEPARTMENT OF

JUSTICE

215 N Sanders, 3rd Floor

Helena, MT 59620

406-444-2026

christian.corrigan@mt.gov

*Counsel of Record

27

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Attorney General of

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Attorney General of

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Attorney General of

Nebraska

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Attorney General of

New Hampshire

DREW H. WRIGLEY

Attorney General of

North Dakota

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Attorney General of Ohio

28

GENTNER F. DRUMMOND

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Attorney General of

South Carolina

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Reporter of Tennessee

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