Governor Meyer Joins Multi-State Brief on Assault Weapons Restrictions

October 28, 2026/Joe Ciccanti

Delaware Governor Matt Meyer has joined governors from eight other states in filing a brief with the U.S. Supreme Court urging it to uphold state and local laws restricting assault weapons. The brief argues states should retain the authority to enact gun safety measures to address public safety concerns. The court is considering challenges to assault weapons restrictions in Illinois and elsewhere. Meyer established Delaware’s Office of Gun Violence Prevention and Community Safety in May 2025; the office was later made permanent through legislation.

Additional Information from the Office of Governor Matt Meyer:

Governor Meyer joined the Safer Communities Initiative alongside Governors Gavin Newsom of California, Jared Polis of Colorado, JB Pritzker of Illinois, Wes Moore of Maryland, Kathy Hochul of New York, Tina Kotek of Oregon, Dan McKee of Rhode Island and Bob Ferguson of Washington.

Nos. 25-238 & 25-566

In the Supreme Court of the United States

CUTBERTO VIRAMONTES, ET AL., PETITIONERS v.

COOK COUNTY, ILLINOIS, ET AL.

EDDIE GRANT JR., ET AL., PETITIONERS

RONNELL HIGGINS, IN HIS OFFICIAL CAPACITY AS COMMISSIONER OF THE CONNECTICUT DEPARTMENT OF EMERGENCY SERVICES AND PUBLIC PROTECTION, ET AL.

ON WRITS OF CERTIORARI TO THE UNITED STATES COURTS OF APPEALS FOR THE SEVENTH AND SECOND CIRCUITS

BRIEF OF THE GOVERNORS SAFER

COMMUNITIES INITIATIVE AS AMICUS CURIAE IN SUPPORT OF RESPONDENTS

STEPHEN K. WIRTH

Counsel of Record

JACOBSON LAWYERS GROUP PLLC

5100 Wisconsin Avenue NW Suite 301

Washington, DC 20016

(406) 407-6051

stephen@jacobsonlawyers group.com

KARIANNE JONES

GRACE LEEPER

EVERGREEN LEGAL

STRATEGIES LLP

1763 Columbia Road NW Suite 100

Washington, DC 20009

JULIA SPIEGEL

EMILY F. KIRBY

CHARANYA KRISHNASWAMI ALISON SHIH

MEGAN FLYNN

GOVERNORS ACTION

ALLIANCE

2300 N Street NW, Suite 501A Washington, DC 20007

TABLE OF CONTENTS

Page

Interest of Amicus Curiae…………………………………………..1 Introduction and Summary of Argument……………………..2 Argument……………………………………………………………………3 I. Amicus Members Have Directly Confronted the

Human Costs and Operational Consequences of Assault-Weapon Violence……………………………………….3 A. Amicus member governors have personally

experienced the human toll of assault-weapon violence in their own states ……………………………….3 B. Mass shootings involving assault weapons impose severe, lasting operational burdens on amicus members’ jurisdictions………………………….9 II. Assault Weapons Make Mass Shootings More Lethal, and Safety Measures Regulating Them Work ……………………………………………………………………17 A. Assault weapons are distinctively dangerous, and safety laws regulating their use save lives…17 B. States have adopted a range of firearm

measures to promote the safety and well-being of residents……………………………………………………..23 Conclusion…………………………………………………………………28

TABLE OF AUTHORITIES

Cases:

Bianchi v. Brown,

111 F.4th 438 (4th Cir. 2024)…………… 17, 19, 21, 23, 28 Capen v. Campbell,

No. 22-cv-11431, 2023 WL 8851005 (D. Mass. Dec. 21, 2023)……………………………………………………….21

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Cases—Continued: Page

Del. State Sportsmen’s Ass’n v. Del. Dep’t of Safety & Homeland Sec.,

664 F. Supp. 3d 584 (D. Del. 2023)…………………………21 Duncan v. Bonta,

133 F.4th 852 (9th Cir. 2025)…………………………………18 Gonzales v. Oregon,

546 U.S. 243 (2006)………………………………………….23, 27 Kolbe v. Hogan,

849 F.3d 114 (4th Cir. 2017) …………………………….17, 18 Nat’l Ass’n for Gun Rts. v. Lamont,

153 F.4th 213 (2d Cir. 2025) ………………………………….24 New State Ice Co. v. Liebmann,

285 U.S. 262 (1932)……………………………………………….28 N.Y. State Rifle & Pistol Ass’n, Inc. v. Bruen, 597 U.S. 1 (2022)……………………………………………..17, 20 Ocean State Tactical, LLC v. Rhode Island, 95 F.4th 38 (1st Cir. 2024) ……………………………….18, 19 Or. Firearms Fed’n v. Kotek,

682 F. Supp. 3d 874 (D. Or. 2023) ………………………….19 Rupp v. Bonta,

723 F. Supp. 3d 837 (C.D. Cal. 2024)………………..19, 21 Worman v. Healey,

922 F.3d 26 (1st Cir. 2019)…………………………………….20

Federal statutes:

18 U.S.C. § 921(a)(31) (1994)……………………………………18 Public Safety and Recreational Firearms Use Protection Act, Pub. L. No. 103-322, tit. XI, subtit. A, §§ 110101–110106, 108 Stat. 1796, 1996–2000 (1994)…………………………………………………..24

III

State statutes, bills & ordinances: Page

Cal. Penal Code

§ 30500–30515 …………………………………………………….24 § 30600 …………………………………………………………………24 § 30605 …………………………………………………………………24 Conn. Gen. Stat.
53-202a………………………………………………………………18 § 53-202b………………………………………………………………24 § 53-202c ………………………………………………………………24 § 53-202d………………………………………………………………24 § 53-202w(b)…………………………………………………………24 Del. Code Ann. tit. 11
1465 …………………………………………………………………..25 § 1466(a) ………………………………………………………………25 § 1468 …………………………………………………………………..25 § 1469(a) ………………………………………………………………25 720 Ill. Comp. Stat. Ann.

5/24-1.9…………………………………………………………………26 5/24-1.10……………………………………………………………….26 Protect Illinois Communities Act, Pub. Act 102- 1116 (Ill. 2023)………………………………………………………26 H.B. 5471, 102nd Gen. Assemb. (Ill. 2022)………………..26 Cook County, Ill., Code of Ordinances

54-211………………………………………………………………..18 § 54-212(a) ……………………………………………………………18 Md. Code Ann., Crim. Law
4-301(d)……………………………………………………………..25 § 4-303(a) ……………………………………………………………..25 § 4-305(b)……………………………………………………………..25

S.F. 4067, 94th Leg., Reg. Sess. (Minn. 2026)…………..27 N.Y. Penal Law

265.00(22)…………………………………………………………..25 § 265.02(7)–(8)………………………………………………………25 R.I. Gen. Laws §§ 11-47.2-1 to -3 (2026) …………………..26

State statutes, bills & ordinances—Continued: Page Act of June 26, 2025, ch. 281, 2025 R.I. Pub. Laws……26 Va. Code Ann. § 18.2-287.4:1(B) ………………………………26 Act of May 14, 2026, ch. 1106, 2026 Va. Acts …………….26 Wash. Rev. Code § 9.41.390……………………………………..26

Federal executive branch materials:

Fed. Sch. Safety Clearinghouse, Low Cost/No Cost Immediately Implementable School Safety Tactics (Dec. 2019)……………………………………………….16

HHS Off. of the Asst. Sec’y for Preparedness & Response (ASPR TRACIE), Trauma Hospitals and Mass Shootings (2018)……………………………..11, 12

Nat’l Ctr. for Educ. Stat., Digest of Education Statistics tbl. 233.65 (2023) …………………………………..16 Off. of the Deputy Att’y Gen., U.S. Dep’t of Just., Overview of Department Law Enforcement Resources for Responding to Critical Domestic Incidents (June 3, 2019) …………………………………………9 Press Release, U.S. Dep’t of Just., Federal Grand Jury Indicts Accused Tops Shooter on Federal Hate Crimes and Firearms Charges in Buffalo, New York (July 14, 2022)………………………………………25 Press Release, U.S. Dep’t of Just., Off. of Pub. Affs., No. 24-782, Former Colorado Resident Sentenced to Life in Prison for Federal Hate Crimes and Firearm Offenses Related to Mass Shooting at Club Q (June 18, 2024)…………………………7 U.S. Fire Admin. & Fed. Emergency Mgmt. Agency, Fire/Emergency Medical Services Department Operational Considerations and Guide for Active Shooter and Mass Casualty Incidents (2013)……………………………………………………..9

State executive branch materials: Page

Del. Gov. Newsroom, Members of the General Assembly Announce Gun Safety Package (June 2, 2022)…………………………………………………………………25

Gavin Newsom (@GavinNewsom), X (Jan. 22, 2023, 8:21 PM PST)………………………………………………..8 Press Release, Off. of Gov. Gavin Newsom, Governor Newsom Proclaims Lunar New Year, Orders Flags to Be Flown at Half-Staff (Jan. 22, 2023)………………………………………………………………………8 Press Release, Off. of Gov. Jared Polis, Governor Jared Polis Orders Flags Lowered to Honor Victims of Colorado Springs Shooting (Nov. 20, 2022)………………………………………………………………………7 Press Release, Off. of Gov. Jared Polis, Governor Jared Polis Releases Statement on Horrific Shooting in Colorado Springs (Nov. 20, 2022) ………..7 Press Release, Off. of Gov. JB Pritzker, Gov. Pritzker Issues Disaster Proclamation to Assist in Recovery Efforts Following Highland Park Mass Shooting (July 5, 2022)…………………………….6, 14 Press Release, Off. of Gov. JB Pritzker, Gov. Pritzker Signs Legislation Banning Assault Weapons and Sale of High-Capacity Magazines (Jan. 10, 2023) ………………………………………………………..6 Press Release, Off. of Gov. JB Pritzker, Gov. Pritzker’s Statement on the Passage of Protect Illinois Communities Act Banning Assault Weapons (Jan. 10, 2023) …………………………………………6 Press Release, Off. of Gov. JB Pritzker, Pritzker Administration Launches Multi-Agency Effort to Bring Additional State Support to Highland Park and Surrounding Areas (July 21, 2022)……6, 14

State executive branch materials—Continued: Page

Press Release, Off. of Gov. Kathy Hochul,

Governor Hochul Announces $2.5 Million in New Funding for Additional Services to

Individuals Impacted by the May 14 White Supremacist Attack at The Tops Market in Buffalo (Mar. 29, 2023) …………………………………………15 Press Release, Off. of Gov. Kathy Hochul,

Governor Hochul Announces State Resources Available for the Buffalo Community in

Response to Horrific Shooting at Tops

Supermarket (May 15, 2022)…………………………………15 Press Release, Off. of Gov. Kathy Hochul,

Governor Hochul Directs Flags to Half-Staff to Honor Victims of Tops Supermarket Shooting in Buffalo (May 15, 2022)……………………………………….5

Press Release, Wash. State Off. of the Att’y Gen., Gov. Inslee Legislation Banning Sale of Assault Weapons Passes House in Historic Vote This Evening (Mar. 8, 2023)………………………….26

Rush Transcript, Off. of Gov. Kathy Hochul, Governor Hochul Addresses Shooting in

Buffalo (May 14, 2022)……………………………………………4 Rush Transcript, Off. of Gov. Kathy Hochul, Governor Hochul Delivers Remarks at

Memorial Service for Healing and Hope (May 14, 2023)…………………………………………………………………5 Brandon Vick et al., Pa. Comm’n on Crime & Delinquency, Cost of Non-fatal Firearm

Injuries in Pennsylvania, 2016–2021 (Aug. 2022)…………………………………………………………………….13

Academic articles & reports:

Gregory DeAngelo et al., Police Response Time and Injury Outcomes, 133 Econ. J. 2147 (2023)…….10

VII

Academic articles & reports—Continued: Page

Charles DiMaggio et al., Changes in US Mass Shooting Deaths Associated with the 1994–2004 Federal Assault Weapons Ban: Analysis of Open-Source Data, 86 J. Trauma & Acute Care Surgery 11 (2019) …………………………………………………22 Charles J. DiMaggio et al., State Assault

Weapons Bans Are Associated with Fewer Fatalities: Analysis of US County Mass

Shooting Incidents (2014–2022), 32 Injury Prevention 317 (2026) …………………………………………..22 Everytown Rsch. & Pol’y, Hurdles to Healing: Removing Barriers to Victim Compensation Funds (Apr. 22, 2021; updated Apr. 20, 2026)………..14 Faiz Gani et al., Emergency Department Visits for Firearm-Related Injuries in the United States, 2006–14, 36 Health Affs. 1729 (2017)………….13 Mark Gius, The Impact of State and Federal Assault Weapons Bans on Public Mass

Shootings, 22 Applied Econ. Letters 281 (2015)…….22 Nikki Graf, A majority of U.S. teens fear a shooting could happen at their school, and most parents share their concern, Pew Rsch. Ctr. (Apr. 18, 2018)………………………………………………………17 IACP Law Enf’t Pol’y Ctr., Active Shooter: Concepts and Issues Paper (updated Apr. 2018) …….9 Katherine M. Kelley et al., Disaster Planning for a Surgical Surge: When Mass Trauma

Threatens to Overwhelm Your Operating

Rooms, Trauma Surgery & Acute Care Open (Nov. 9, 2023) ……………………………………………………….12

VIII

Academic articles & reports—Continued: Page

Michael J. Lozada et al., The Las Vegas Mass Shooting: An Analysis of Blood Component Administration and Blood Bank Donations, J. Trauma & Acute Care Surgery (Oct. 29, 2018)………11 Alex Lars Lundberg et al., Public Mass

Shootings: Counterfactual Trend Analysis of the Federal Assault Weapons Ban, 10 JMIR Pub. Health Surveillance e62952 (2024) ………………..23

Susan F. McLean et al., Report on the El Paso Mass Casualty Incident Hospital Response: Enhancing Surge Capacity, W. J. Emergency Med. (2025)…………………………………………………………..11

Corinne Peek-Asa et al., Cost of Hospitalization for Firearm Injuries by Firearm Type, Intent, and Payer in the United States, 4 Injury

Epidemiology 20 (2017) ………………………………………..13 Lori Post et al., Impact of Firearm Surveillance on Gun Control Policy: Regression

Discontinuity Analysis, 7 JMIR Pub. Health Surveill. e26042 (2021) ………………………………………….22 Tannuja D. Rozario & Paige Tetens, Everytown Rsch. & Pol’y, Assault Weapons and High Capacity Magazines (Mar. 19, 2019, last updated June 24, 2026) ………………………………………………………21 Sarabeth A. Spitzer et al., Readmission Risk and Costs of Firearm Injuries in the United States, 2010–2015, 14 PLOS ONE e0209896 (Jan. 24, 2019)……………………………………………………………….12, 13

News articles:

Steve Almasy, Newtown Shooter’s Guns: What We Know, CNN (Dec. 19, 2012)…………………………….24

News articles—Continued: Page

Aaron C. Davis & Jon Swaine, Suspect in Buffalo Shooting Modified Bushmaster So It Could Hold More Ammunition, Wash. Post (May 15, 2022)…………………………………………………………………….20

Zach Despart, “He Has a Battle Rifle”: Police Feared Uvalde Gunman’s AR-15, Tex. Trib. (Mar. 20, 2023) ……………………………………………………..25

Doug George & Alex Hulvalchick, Highland Park Shooting: List of Other Fourth of July

Fireworks, Events Canceled After Shooting in Chicago Suburb, Chi. Trib. (July 4, 2022) ……………..15 Grocery Store Shooting: 10 People Killed at King Soopers on Table Mesa, CBS News Colorado (Mar. 23, 2021) ………………………………………………..10, 16 Corin Hoggard, Gov. Walz Bypasses Special Session, Issues Executive Orders on Gun

Control, Fox 9 Minneapolis-St. Paul (Dec. 16, 2025)…………………………………………………………………….27 Jessica Hopper et al., Heroes of Tucson Shooting: “Something Had to Be Done,” ABC News (Jan. 10, 2011)……………………………………………………………….19 Elizabeth Ireland & Josh Susong, In Stockton, an Earlier Mass Shooting Brought a Monumental Shift in State Law, Stocktonia (Nov. 30, 2025)………24 Julia Jacobo & Nadine El-Bawab, Timeline: How the Shooting at a Texas Elementary School Unfolded, ABC News (updated Dec. 12, 2022) ………20 Lacey Johnson, Maryland Governor Signs Tough Gun Control Law, Reuters (May 16, 2013) ……………25 Kimberlee Kruesi, Rhode Island’s Assault Weapon Ban Offers a Peek into Why Such Laws Are Difficult to Pass, NBC Bos. (July 5, 2025)………26

News articles—Continued: Page

Frank Main, Illinois State Police director defends decision to give suspected Highland Park killer a gun permit in 2020, Chi. Sun-Times (July 6, 2022)…………………………………………………………………….20

Alanna Mayham, Washington Governor Signs Assault Weapon Sales Ban, Courthouse News Serv. (Apr. 25, 2023)……………………………………………..26 Kayla McCormick & Phil Helsel, El Paso

Walmart Mass Shooter Patrick Crusius

Sentenced to 90 Consecutive Life Terms, NBC News (July 7, 2023) ………………………………………………20 Mark Memmott, “Historic” Gun Bill Becomes Law in Connecticut, NPR (Apr. 4, 2013) ………………24 Monterey Park Shooting: 11 Killed at Lunar New Year Celebration, Suspect Dead from Apparent Self-Inflicted Gunshot Wound, CBS News (updated Jan. 24, 2023, 8:49 PM EST)…………..7 Esme Murphy & Ubah Ali, Minnesota Bill That Would Regulate Ownership, Sale of

Semiautomatic Weapons Passes Senate, CBS News Minn. (May 4, 2026)…………………………………….27 Aki Nace et al., Minneapolis Catholic School Shooting Leaves 2 Children Dead, 21 People Injured, CBS News Minn. (Aug. 27, 2025)…………….27 Aki Nace, Minnesota Legislative Session Ends with No House Vote on Gun Reform Bill, CBS News Minn. (May 18, 2026)…………………………………..27 Reese Oxner, Uvalde Gunman Legally Bought AR Rifles Days Before Shooting, Law

Enforcement Says, Tex. Trib. (May 25, 2022) ……….20

News articles—Continued: Page

Mauricio Peña, After Highland Park shooting, local schools became healing centers to help grieving community, Chalkbeat Chi. (July 11, 2022)…………………………………………………………………….16

Carolyn Phenicie, How Much More Money Are States Spending on School Security After the Parkland Shooting?, The 74 (Aug. 20, 2018) …………16

Olivia Prentzel, Club Q suspect said they were going to run errand, committed mass shooting instead, unsealed court document says, Colo. Sun (Dec. 7, 2022)………………………………………………………….6

Ayesha Rascoe, Weekend Edition Sunday: N.Y. Gov. Kathy Hochul Responds to Shooting in Her Hometown (NPR radio broadcast May 15, 2022)………………………………………………………………………4

Ravinia Cancels Concerts Through Sunday After Mass Shooting in Highland Park, CBS News Chicago (July 2022)………………………………………………15

Robert Crimo III indicted on 117 counts in deadly Highland Park parade shooting,

prosecutors say, ABC7 Chicago (July 27,

2022)……………………………………………………………….25–26 Joel Rose, New York the First State to Pass Gun Control Measures After Newtown Shootings, NPR (Jan. 15, 2013) ……………………………………………..25 Nouran Salahieh et al., Monterey Park,

California Shooting: 11 Victims Ranged in Age from 57 to 76 Years Old, Coroner Says, CNN (Jan. 24, 2023) ………………………………………………………..7 Jared Serre, Assault Weapons Ban Could Have New Path Forward Under Gov. Spanberger, Lawmakers Say, ARLnow (Jan. 12, 2026)…………….26

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News articles—Continued: Page

Several 4 July Events Canceled in Wake of Highland Park Parade Shooting, CBS News Chicago (July 4, 2022)…………………………………………..15

Steven Spearie, Gov. JB Pritzker ‘‘Furious;’’ Other Illinois Officials React to Highland Park Shooting, State J.-Reg. (July 4, 2022)……………………..5 David Struett, Suspect in Highland Park

massacre pleads not guilty to 117 charges. Parents say they ‘deeply regret the actions’ of their son, Chi. Sun-Times (July 6, 2022)………………….5

Alex Sundby & Jordan Freiman, At Least 7 Killed in Shooting at Fourth of July Parade in Highland Park, Illinois; Person of Interest in Custody, CBS News (July 5, 2022)………………………..10

Carolyn Thompson & Michael Balsamo, Buffalo Shooter Targeted Black Neighborhood, Officials Say, Longview News-Journal (May 16, 2022)………….4

Amanda Vinicky, Local Legislators Spent Years Trying to Pass Gun Laws. After Highland Park’s Deadly Parade Shooting, Illinois Took Action, WTTW News (July 3, 2023)………………………25

What We Know About the El Paso and Dayton Shooters’ Guns, PBS NewsHour (Aug. 6, 2019)…….20 Craig Whitlock et al., Suspect in Buffalo Shooting Modified Bushmaster So It Could Hold More Ammunition, Wash. Post (May 15, 2022) ……………….4 Deena Winter & Paul Walsh, Suspected Shooter Legally Purchased Rifle, Pistol and Shotgun; Local Politicians Call for Action, Star Trib. (Aug. 28, 2025) ……………………………………………………..27

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News articles—Continued: Page

Caitlin Yilek, Gavin Newsom After Monterey Park Shooting: “Second Amendment Is

Becoming a Suicide Pact,” CBS News (Jan. 23, 2023)………………………………………………………………………8 Olivia Young, Governor Jared Polis Visits Club Q Memorial: “The Community Will Be Back and People Will Feel Safe,” CBS Colo. (Nov. 29, 2022)…..7

INTEREST OF AMICUS CURIAE

The Governors Safer Communities Initiative brings together governors who are committed to championing whole-of-government strategies that build safer commu nities and prevent gun violence in their respective juris dictions.1 Governors formed the Safer Communities Ini tiative to implement innovative cross-state approaches to keeping their communities safe.

The Governors Safer Communities Initiative includes California Governor Gavin Newsom, Colorado Governor Jared Polis, Delaware Governor Matt Meyer, Illinois Gov ernor JB Pritzker, Maryland Governor Wes Moore, Min nesota Governor Tim Walz, New York Governor Kathy Hochul, Oregon Governor Tina Kotek, Rhode Island Gov ernor Daniel McKee, Virginia Governor Abigail Span berger, and Washington Governor Bob Ferguson. Given its priorities, the Initiative’s members have a significant interest in the defense of common-sense measures that regulate possession of certain dangerous weapons. Al though the laws of amicus members’ jurisdictions differ in substance, we are aligned in our firm conviction that states retain broad authority under their police power to enact measures like these—tailored to their own resi dents’ needs and consistent with our Nation’s historical tradition. The officials who enact them, moreover, are best positioned to judge what their communities need.

Amicus members’ jurisdictions have confronted, firsthand, the human and operational consequences of mass shootings committed with assault weapons—in New York, at Buffalo; in Illinois, at Highland Park; in Colo

rado, at Colorado Springs; in California, at Monterey

1 No counsel for a party authored this brief in whole or in part. No person or entity, other than amicus or its counsel, made a monetary contribution intended to fund the preparation or submission of this brief.

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Park, and in other Initiative members’ jurisdictions that have lived through similar tragedies. As the chief execu tives responsible for their states’ emergency response, public health, and victim-services systems, amicus mem bers write to provide the Court with a firsthand account of what these shootings have cost their communities, and why the laws at issue reflect a considered, evidence-based response to a real and recurring threat to public safety.

INTRODUCTION AND SUMMARY OF ARGUMENT For the governors of the Safer Communities Initia tive, the question presented in this case is not an academic one. Amicus governors have had to decide, in the days and weeks after an assault-weapon attack in their own state, how to mobilize the human and financial capacity to respond to a tragedy no community should have to en dure. Four such attacks are recounted below from the perspective of the chief executives responsible for the safety of their communities.

Virtually all of amicus members’ jurisdictions have experienced a mass shooting—in their houses of worship, grocery stores, suburban malls, schools—bearing the bur den of law-enforcement mobilization, emergency medical care, victim compensation, and a disruption to community life reaching well beyond the shooting scene itself. These costs are neither speculative nor short-lived. State re

sponse to mass shootings alone runs into the hundreds of millions of dollars nationwide; the broader cost of treating firearm injuries reaches into the billions. Both continue long after the headlines fade.

The extraordinary human and financial toll is a direct consequence of what assault weapons are built to do. These are weapons explicitly designed for the battlefield, adopted by the U.S. military in the 1960s and still in use to this day. These weapons are outfitted for our troops with the features included in the Cook County Ordinance

and Connecticut Statute at additional expense, because of the express tactical advantages that give them a capacity for mass casualties far exceeding that of an ordinary fire arm. States and the federal government have regulated these weapons for decades, frequently in direct response to the kind of tragedy amicus governors describe below, and the empirical record confirms that legislative judg ment: jurisdictions that have enacted assault-weapons safety measures experience fewer, and less lethal, mass shootings than those that have not.

Taken together, amicus governors’ firsthand experi ence and the empirical record confirm that the Cook County Ordinance at issue in this case and the Connecti cut law at issue in the companion case reflect precisely the kind of considered, evidence-based judgment that the Constitution—from the founding to the modern era— leaves to the states’ traditional police power. The judg ments below should be affirmed.

ARGUMENT

Amicus Members Have Directly Confronted the Human Costs and Operational Consequences of Assault-Weapon Violence
Amicus member governors have personally experienced the human toll of assault-weapon violence in their own states

The overwhelming majority of Governors Safer Com munities Initiative members’ jurisdictions have experi enced a mass shooting—the victims were their own neigh bors, coworkers, and classmates. Governors were called

to answer these attacks with the emergency responders, hospitals, and victim-services systems their states had built. The accounts that follow recount several such trag edies and the devastation they caused, from the perspec tive of the state’s chief executive charged with keeping its residents safe.

On May 14, 2022, an eighteen-year-old gunman drove more than three hours from his home in Conklin, New York, to a Tops Friendly Market on Jefferson Ave nue in Buffalo, deliberately targeting a supermarket in the city’s predominantly Black East Side neighborhood.2 He was armed with an assault rifle that he had illegally modified to accept a large-capacity magazine.3 In roughly six minutes, he killed ten people—all of them Black—and wounded three others.4

On the day of the attack, Governor Kathy Hochul, a Buffalo native, told reporters, “This is my community. I know this community well, I’ve walked these streets.”5 She described a neighborhood’s “sense of security shat

tered” by a “military style execution,” targeting people who simply wanted to buy groceries.6 The next day, she spoke of the “excruciatingly painful process” of identify ing the victims and notifying their families7and ordered flags lowered statewide, declaring that “[a]n attack on one

2 Carolyn Thompson & Michael Balsamo, Buffalo Shooter Targeted Black Neighborhood, Officials Say, Longview News-Journal (May 16, 2022), https://perma.cc/8W2F-9EJ6.

3 See Craig Whitlock et al., Suspect in Buffalo Shooting Modified Bushmaster So It Could Hold More Ammunition, Wash. Post (May 15, 2022), https://bit.ly/4yP8TQp.

4Ibid.

5 Rush Transcript, Off. of Gov. Kathy Hochul, Governor Hochul Ad dresses Shooting in Buffalo (May 14, 2022), https://perma.cc/YYX7- 2V7J.

6Ibid.

7 Ayesha Rascoe, Weekend Edition Sunday: N.Y. Gov. Kathy Hochul Responds to Shooting in Her Hometown (NPR radio broadcast May 15, 2022) (transcript), https://n.pr/4yIMvIw.

of us is an attack on all of us.”8 On the one-year anniver sary of the shooting, she walked through the Tops after the afternoon remembrance and came upon a family sob bing; within the sobs, she heard, “I miss my mom. I want my mom here.”9 She told the community that the work is not done “as long as assault weapons intended for the bat tlefield are still allowed to be sold in this country.”10

On July 4, 2022, a gunman climbed a ladder to a rooftop overlooking Highland Park, Illinois’s Fourth of July parade route, then opened fire on the crowd below. He was armed with an assault rifle fed by three 30-round magazines.11 In under a minute, he fired eighty-three rounds, killing seven people and wounding forty-eight others.12 The victims ranged in age from eight to eighty eight.

Governor JB Pritzker immediately responded, noting that he was “furious that yet more innocent lives were taken by gun violence.”13 The next day, he issued a disas

8 Press Release, Off. of Gov. Kathy Hochul, Governor Hochul Directs Flags to Half-Staff to Honor Victims of Tops Supermarket Shooting in Buffalo (May 15, 2022), https://perma.cc/LW36-DXPA. 9 Rush Transcript, Off. of Gov. Kathy Hochul, Governor Hochul De livers Remarks at Memorial Service for Healing and Hope (May 14, 2023), https://perma.cc/TN8E-MERK.

10 Ibid.

11 See David Struett, Suspect in Highland Park massacre pleads not guilty to 117 charges. Parents say they ‘deeply regret the actions’ of their son, Chi. Sun-Times (July 6, 2022), https://perma.cc/WT73- BL4P.

12 Ibid.

13 Steven Spearie, Gov. JB Pritzker ‘‘Furious;’’ Other Illinois Offi cials React to Highland Park Shooting, State J.-Reg. (July 4, 2022), https://perma.cc/BU48-S4P2.

ter proclamation for Lake County, which includes High land Park,14 and within weeks, the State had launched a multi-agency effort to support Highland Park and sur rounding areas.15 When the General Assembly passed the Protect Illinois Communities Act six months after the at tack, Governor Pritzker said that “for too long people have lived in fear of being gunned down in schools, while worshipping, at celebrations or in their own front yards.”16 He vowed to keep fighting “to ensure that future genera tions only hear about massacres like Highland Park, Sandy Hook, and Uvalde in their textbooks.”17

On November 19, 2022, an individual wearing a bal listic vest walked into Club Q, a nightclub in Colorado Springs, Colorado, that serves as a gathering place for the city’s LGBTQ community.18 The shooter, armed with an assault rifle, opened fire and kept firing until patrons of

14 Press Release, Off. of Gov. JB Pritzker, Gov. Pritzker Issues Dis aster Proclamation to Assist in Recovery Efforts Following High land Park Mass Shooting (July 5, 2022), https://perma.cc/CZH8- Y3EZ.

15 Press Release, Off. of Gov. JB Pritzker, Pritzker Administration Launches Multi-Agency Effort to Bring Additional State Support to Highland Park and Surrounding Areas (July 21, 2022), https:// perma.cc/8553-BHYM.

16 Press Release, Off. of Gov. JB Pritzker, Gov. Pritzker’s Statement on the Passage of Protect Illinois Communities Act Banning Assault Weapons (Jan. 10, 2023), https://perma.cc/28F9-QN5S. 17 Press Release, Off. of Gov. JB Pritzker, Gov. Pritzker Signs Legis lation Banning Assault Weapons and Sale of High-Capacity Maga zines (Jan. 10, 2023), https://perma.cc/2Q7H-CMWS. 18 Olivia Prentzel, Club Q suspect said they were going to run errand, committed mass shooting instead, unsealed court document says, Colo. Sun (Dec. 7, 2022), https://perma.cc/GH9Y-C89F.

the club subdued him.19 The shooter killed five people and injured nineteen others.

Governor Jared Polis told Colorado Springs’ mayor that “every state resource is available to local law enforce ment,” and he thanked both the patrons who blocked the gunman and the first responders who arrived swiftly.20 Governor Polis ordered flags lowered on all public build ings statewide for five days, one for each person killed.21 Visiting the memorial days later, he promised that “Club Q will be back and the community will be back.”22

On the evening of January 21, 2023, a gunman en tered the Star Ballroom Dance Studio in Monterey Park, California, where patrons had gathered to dance.23 The eve of Lunar New Year, a day of celebration for Monterey Park’s majority-Asian population, quickly turned to trag edy.24 The gunman was armed with an assault pistol fitted

19 Press Release, U.S. Dep’t of Just., Off. of Pub. Affs., No. 24-782, Former Colorado Resident Sentenced to Life in Prison for Federal Hate Crimes and Firearm Offenses Related to Mass Shooting at Club Q (June 18, 2024), https://bit.ly/4soKEa1.

20 Press Release, Off. of Gov. Jared Polis, Governor Jared Polis Re leases Statement on Horrific Shooting in Colorado Springs (Nov. 20, 2022), https://perma.cc/Y27P-CYQK.

21 Press Release, Off. of Gov. Jared Polis, Governor Jared Polis Or ders Flags Lowered to Honor Victims of Colorado Springs Shooting (Nov. 20, 2022), https://perma.cc/84DS-3DWA.

22 Olivia Young, Governor Jared Polis Visits Club Q Memorial: “The Community Will Be Back and People Will Feel Safe,” CBS Colo. (Nov. 29, 2022), https://perma.cc/EW6P-SSQB.

23 Monterey Park Shooting: 11 Killed at Lunar New Year Celebra tion, Suspect Dead from Apparent Self-Inflicted Gunshot Wound, CBS News (updated Jan. 24, 2023, 8:49 PM EST), https:// perma.cc/G6YV-98NB.

24 Nouran Salahieh et al., Monterey Park, California Shooting: 11 Victims Ranged in Age from 57 to 76 Years Old, Coroner Says, CNN (Jan. 24, 2023), https://cnn.it/4soEmaq.

with an extended magazine, firing forty-two rounds that killed eleven people and wounded nine others.25

The next day, Governor Gavin Newsom issued a proc lamation recognizing Lunar New Year as an official state holiday and ordered that flags at state buildings be flown at half-staff in honor of the victims.26 In the proclamation, Governor Newsom explained that “[n]o one should have to fear for their life while gathering in their community,” and pledged that “California will continue to lead the charge to end the epidemic of senseless gun violence and protect [its] diverse communities.”27 That same day, Gov

ernor Newsom spent time in Monterey Park meeting with community members, writing that “[t]he strength of this community is incredible.”28 The following day, he said of the attack: “Nothing about this is surprising. Everything about this is infuriating.”29

25 Ibid. Although the assault pistol used in the Monterey Park shoot ing is not identical to the weapons restricted by the Cook County and Connecticut safety measures at issue in this case, amicus provides this example to highlight the human toll borne by states in the wake of mass shootings—which, as discussed infra Section II.A, are dis proportionately committed with assault weapons.

26 Press Release, Off. of Gov. Gavin Newsom, Governor Newsom Pro claims Lunar New Year, Orders Flags to Be Flown at Half-Staff (Jan. 22, 2023), https://perma.cc/3C23-ZUZA.

27 Ibid.

28 Gavin Newsom (@GavinNewsom), X (Jan. 22, 2023, 8:21 PM PST), https://perma.cc/63HL-ENRT.

29 Caitlin Yilek, Gavin Newsom After Monterey Park Shooting: “Sec ond Amendment Is Becoming a Suicide Pact,” CBS News (Jan. 23, 2023), https://perma.cc/RMZ9-5AU3.

Mass shootings involving assault weapons impose severe, lasting operational burdens on amicus members’ jurisdictions
Responding to a mass shooting often requires an extraordinary, multi-agency law enforcement mobiliza tion far exceeding the resources needed for an ordinary call for service. That mobilization follows established pro tocols:30 the first arriving officers make immediate entry; federal agencies may provide tactical, intelligence, and fo rensic support in the incident’s aftermath;31 fire and EMS personnel may begin life-saving care before the scene is fully cleared,32 all coordinated through a unified incident command post. Mass shootings can therefore require dozens, or even hundreds, of law enforcement and emer gency personnel to respond to the scene.

Amicus members’ own experience confirms the point. For example, the Highland Park shooting and a 2021 mass shooting at a Boulder grocery store both drew a massive, multi-agency response that utilized an outsized number of state resources. At Highland Park, over 100 law enforcement officers from multiple agencies re

sponded to the scene and worked diligently over the course of the next nine hours to track down and arrest the

30 IACP Law Enf’t Pol’y Ctr., Active Shooter: Concepts and Issues Paper (updated Apr. 2018), https://perma.cc/V795-9GWL. 31 Off. of the Deputy Att’y Gen., U.S. Dep’t of Just., Overview of De partment Law Enforcement Resources for Responding to Critical Domestic Incidents (June 3, 2019), https://perma.cc/GN4T-3NZG. 32 U.S. Fire Admin. & Fed. Emergency Mgmt. Agency, Fire/Emer gency Medical Services Department Operational Considerations and Guide for Active Shooter and Mass Casualty Incidents (2013), https://perma.cc/3LSQ-33KU.

shooter.33 In Boulder, after ten people (including one po lice officer) were killed at a King Soopers grocery store, hundreds of police and first responders sped to the scene, including Boulder Police Department, Jefferson County SWAT, Lakewood Police, Denver Police, and FBI Den ver.34

A mass shooting does not merely burden a state’s emergency-response system; it also erodes the protection available to everyone else the state’s police and paramed ics are there to serve. Every officer dispatched to a mass shooting is an officer unavailable to respond to other ur gent calls for service—domestic violence, burglaries, wel fare checks—that continue to occur in the jurisdiction while the shooting is underway. Every ambulance or fire engine dispatched is, in the same way, one less resource available for the heart attack, house fire, or car accident happening elsewhere.

Indeed, peer-reviewed research confirms that when fewer police vehicles are available near a given call—pre cisely the condition created when resources are concen trated at the scene of a mass shooting—response times to other calls lengthen, and longer response times increase the likelihood of injury to the people waiting for help.35 In these circumstances, then, governors are often in the po sition of making difficult decisions about resource alloca tions.

33 Alex Sundby & Jordan Freiman, At Least 7 Killed in Shooting at Fourth of July Parade in Highland Park, Illinois; Person of Interest in Custody, CBS News (July 5, 2022), https://perma.cc/N25Z-4L3W. 34 Grocery Store Shooting: 10 People Killed at King Soopers on Table Mesa, CBS News Colorado (Mar. 23, 2021), https://perma.cc/298M DDRR.

35 See Gregory DeAngelo et al., Police Response Time and Injury Outcomes, 133 Econ. J. 2147 (2023), https://bit.ly/4BN0Czl.

Mass shootings also place a severe strain on state medical systems overseen by the state’s chief executive, lasting from the moment victims reach the hospital to long after the immediate crisis passes. A single mass shooting can overwhelm a trauma center’s emergency depart

ments and operating rooms within minutes. After the 2016 Pulse Nightclub shooting in Orlando, Florida, for ex ample, the first 36 patients arrived in 36 minutes, a “vol ume of patients” that one treating physician said made standard triage “impossible.”36 The same goes for El Paso, after the Walmart shooting in 2019: a single trauma center admitted 14 people within approximately the first half hour, and over 130 people from 16 departments were called in to provide surge capacity to the trauma team.37

That surge of patients can quickly exhaust a region’s blood supply and surgical capacity. The increased blood resource needs in the wake of a mass shooting often re quire a hospital to rely on supplementation from local blood suppliers or national resources like the United Blood Services or American Red Cross.38 Even where hospitals are able to work with local blood banks or na tional suppliers to secure enough blood to meet their im

36 HHS Off. of the Asst. Sec’y for Preparedness & Response (ASPR TRACIE), Trauma Hospitals and Mass Shootings (2018) (interview with John Hick, M.D., and others), https://perma.cc/TB2U-3CZW. 37 Susan F. McLean et al., Report on the El Paso Mass Casualty In cident Hospital Response: Enhancing Surge Capacity, W. J. Emer gency Med. (2025), https://bit.ly/4A0g4X2.

38 See Michael J. Lozada et al., The Las Vegas Mass Shooting: An Analysis of Blood Component Administration and Blood Bank Do nations, J. Trauma & Acute Care Surgery (Oct. 29, 2018), https://bit.ly/4spdE1m; ASPR TRACIE, supra note 36.

mediate needs, the region’s blood supply can remain de pleted in the aftermath.39 The result is a shortage that outlasts the shooting itself.

The need to perform multiple simultaneous emer gency surgeries on mass-shooting victims can force hospi tals to postpone other patients’ scheduled procedures and reassign rooms that would otherwise be in use.40 Follow ing the Pulse Nightclub shooting, for example, one hospi tal’s trauma center expanded from two operating rooms to eight within two hours to accommodate the surge in pa tients.41

The financial burden does not end at patient dis charge: within six months of an initial firearm-injury hos pitalization, 15.6% of survivors are readmitted—most within the first thirty days—adding a further $517 million in costs nationwide on top of the initial hospitalization over the course of 2010 to 2015.42 One study found that fire arm-related emergency department visits nationwide be tween 2006 and 2014 generated nearly $2.8 billion per year in combined emergency-department and inpatient

39 ASPR TRACIE, supra note 36 (Colorado physician noting that “We were able to work with our blood donation site to get what we needed, but the region was definitely depleted for a few weeks after.”). 40 See Katherine M. Kelley et al., Disaster Planning for a Surgical Surge: When Mass Trauma Threatens to Overwhelm Your Operat ing Rooms, Trauma Surgery & Acute Care Open (Nov. 9, 2023), https://bit.ly/3U5bSpI (plans “predominantly focus[] on mass casu alty care in the emergency department,” leaving a documented gap for simultaneous urgent surgery demand).

41 See ASPR TRACIE, supra note 36.

42 See Sarabeth A. Spitzer et al., Readmission Risk and Costs of Fire arm Injuries in the United States, 2010–2015, 14 PLOS ONE e0209896 (Jan. 24, 2019).

charges.43 The type of weapon itself drives the cost pre mium. According to one study, hospitalizations involving assault weapons specifically average $32,237 per admis sion—the highest of any firearm type studied.44

The financial burden lands on individual hospitals and the public insurance programs that stand behind unin sured and underinsured patients. Medicaid alone pays for 38.1%—roughly $2.1 billion—of all costs associated with firearm-injury hospitalizations nationwide.45 For exam ple, between 2016 and 2021, Pennsylvania’s hospitals treated an estimated 10,640 nonfatal firearm injuries at a cost of over $300 million for initial care alone.46 Sixty-five percent of those visits were submitted to Medicaid, which the Commonwealth funds jointly with the federal govern ment.47 By 2020, government-funded plans bore more than 80% of the costs of those injuries—well above the roughly 50% share that government carries across U.S. health spending generally.48

Victim compensation, crisis counseling, and other victim-services spending in the wake of mass shootings poses a real burden on the state fisc. The federal govern ment’s victim-compensation funding structure recognizes

43 See Faiz Gani et al., Emergency Department Visits for Firearm Related Injuries in the United States, 2006–14, 36 Health Affs. 1729 (2017).

44 See Corinne Peek-Asa et al., Cost of Hospitalization for Firearm Injuries by Firearm Type, Intent, and Payer in the United States, 4 Injury Epidemiology 20 (2017).

45 See Spitzer et al., supra note 42.

46 See Brandon Vick et al., Pa. Comm’n on Crime & Delinquency, Cost of Non-fatal Firearm Injuries in Pennsylvania, 2016–2021, at 1, 7, 22–23 (Aug. 2022).

47 Ibid.

48 Ibid.

mass shootings as a state fiscal obligation but only pro vides partial reimbursement for state spending on these crucial services. Under the Victims of Crime Act, the fed eral government reimburses states for just $0.75 of every $1 they spend on victim compensation, paid out two years later—leaving both the remainder of the cost and the im mediate cash-flow burden squarely on the states.49 For fiscal year 2023, for example, states and territories paid out roughly $238.6 million in victim-compensation claims from their own funds—of which the federal government reimbursed only about $179 million two years later, leav ing states to bear the remaining $59.7 million them selves.50

Illinois’s response to the 2022 Highland Park shoot ing illustrates the point. Within a day, Governor JB Pritz ker had issued a state disaster proclamation, making ad ditional state resources available to assist recovery ef forts.51 Within three weeks, a multi-agency state effort

was delivering crisis counseling through the Department of Healthcare and Family Services’ Medicaid managed care organizations and the Department of Human Ser vices, emergency financial assistance for residents whose employers had closed, and interpretation and bilingual services.52

49 See Everytown Rsch. & Pol’y, Hurdles to Healing: Removing Bar riers to Victim Compensation Funds (Apr. 22, 2021; updated Apr. 20, 2026), https://perma.cc/X7WD-HQEE.

50 Ibid.

51 Press Release, Off. of Gov. JB Pritzker, Gov. Pritzker Issues Dis aster Proclamation to Assist in Recovery Efforts Following High land Park Mass Shooting (July 5, 2022).

52 See Press Release, Off. of Gov. JB Pritzker, Pritzker Administra tion Launches Multi-Agency Effort to Bring Additional State Sup port to Highland Park and Surrounding Areas (July 21, 2022).

As New York’s response to the 2022 Buffalo shooting shows, moreover, this obligation does not end with an ini tial burst of aid. The State committed $2.8 million in com bined federal and state funding within days, covering vic tim compensation, crisis counseling, and rideshare access for the affected community.53 Nearly a year later, the State committed a further $2.5 million to sustain those services through June 2025—evidence that a mass shoot ing’s victim-services burden extends well beyond the im mediate aftermath.54

Mass shootings also impose disruptions on commu nities well beyond the scene of the shooting. The 2022 Highland Park parade shooting affected community events city-wide: surrounding suburbs canceled their own Independence Day festivities and the Chicago White Sox played their scheduled game “with a moment of silence and without the postgame fireworks.”55 The nearby Ravinia Festival, which is the longest-running outdoor music festival in North America, canceled or postponed its concerts through the following Sunday.56

53 See Press Release, Off. of Gov. Kathy Hochul, Governor Hochul Announces State Resources Available for the Buffalo Community in Response to Horrific Shooting at Tops Supermarket (May 15, 2022). 54 See Press Release, Off. of Gov. Kathy Hochul, Governor Hochul Announces $2.5 Million in New Funding for Additional Services to Individuals Impacted by the May 14 White Supremacist Attack at The Tops Market in Buffalo (Mar. 29, 2023).

55 Several 4 July Events Canceled in Wake of Highland Park Parade Shooting, CBS News Chicago (July 4, 2022); Doug George & Alex Hulvalchick, Highland Park Shooting: List of Other Fourth of July Fireworks, Events Canceled After Shooting in Chicago Suburb, Chi. Trib. (July 4, 2022), https://perma.cc/V7LR-JNNG.

56 Ravinia Cancels Concerts Through Sunday After Mass Shooting in Highland Park, CBS News Chicago (July 2022), https:// perma.cc/2D65-YSS2.

Schools in particular absorb a significant share of this burden, whether or not a shooting occurs on campus. In the wake of the Highland Park shooting, the local school district converted two high schools into trauma and coun

seling centers, serving about 600 people in the days fol lowing the tragedy.57 In 2018, following the Parkland shooting alone, twenty-six states increased school-safety spending by “at least $950 million.”58 Even where a shoot ing does not occur at a school, educational resources may be affected. After the 2021 Boulder shooting, for exam ple, the University of Colorado Boulder canceled evening classes while nearby Boulder High School was placed on “secure lockout.”59

The repeated threat takes a toll on students. In the 2021–2022 school year, 95.5% of public schools drilled stu dents on lockdown procedures.60 Students rehearse hid ing from an armed intruder, and classrooms are arranged with that possibility in mind: federal guidance advises teachers to identify a corner out of the line of sight from the classroom door and to be able to cover the door win dow.61 Widespread worry accompanies this preparation,

57 Mauricio Peña, After Highland Park shooting, local schools became healing centers to help grieving community, Chalkbeat Chi. (July 11, 2022), https://perma.cc/9G3A-PNJB.

58 Carolyn Phenicie, How Much More Money Are States Spending on School Security After the Parkland Shooting?, The 74 (Aug. 20, 2018), https://perma.cc/WB79-9BB9.

59 Grocery Store Shooting: 10 People Killed at King Soopers on Table Mesa, CBS News Colorado (Mar. 23, 2021), https://perma.cc/D2HW TFN6.

60 Nat’l Ctr. for Educ. Stat., Digest of Education Statistics tbl. 233.65 (2023), https://perma.cc/ACJ4-E7MX.

61 Fed. Sch. Safety Clearinghouse, Low Cost/No Cost Immediately Implementable School Safety Tactics (Dec. 2019), https:// perma.cc/C9QA-GJTY.

with more than half of all teens reporting they were wor ried about a shooting at their school in a 2018 survey.62

The result, then, is a burden that reaches far beyond the shooting scene itself—disrupting community life in the immediate aftermath and leaving states to shoulder costs for years afterward.

Assault Weapons Make Mass Shootings More Lethal, and Safety Measures Regulating Them Work
Assault weapons are distinctively dangerous, and safety laws regulating their use save lives
Assault weapons are firearms engineered with a specific set of combat-functional features that, taken to gether, produce a “capability for lethality—more wounds, more serious, in more victims—far beyond that of other firearms in general, including other semiautomatic guns.” Bianchi v. Brown, 111 F.4th 438, 453 (4th Cir. 2024) (en banc), cert. denied sub nom. Snope v. Brown, 145 S. Ct. 1534 (2025) (quoting Kolbe v. Hogan, 849 F.3d 114, 125 (4th Cir. 2017) (en banc), abrogated on other grounds by N.Y. State Rifle & Pistol Ass’n, Inc. v. Bruen, 597 U.S. 1 (2022)). The AR-15 sold to civilians today is the paradigmatic example. That weapon was explicitly de

signed for the battlefield, with “combat-functional fea tures” including a flash suppressor (to conceal the shooter’s position), a pistol grip (to “enable fast reloading and accuracy” during prolonged firing), and exceptional firepower (to pierce helmets and body armor). See Bian chi, 111 F.4th at 454–456.

The ability to accept a large-capacity magazine (LCM) frequently plays an integral part in the assault

62 Nikki Graf, A majority of U.S. teens fear a shooting could happen at their school, and most parents share their concern, Pew Rsch. Ctr. (Apr. 18, 2018), https://perma.cc/2NFU-KRTG.

weapon’s design.63 Assault weapons are often defined as semiautomatic firearms capable of accepting a detachable magazine, meaning a shooter can insert any compatible magazine, and having certain other specified features. An LCM is an ammunition-feeding device that has the capac

ity to accept more than a specified number of rounds— historically ten, including under the now-expired federal definition. See 18 U.S.C. § 921(a)(31) (1994).

Many assault weapons “are capable of accepting mag azines of thirty, fifty, or even 100 rounds.” Kolbe, 849 F.3d at 125. As a result, “LCMs enable semiautomatic weap ons to function even more like their … automatic counter parts: Both M-16s and semiautomatic firearms equipped with LCMs can rapidly hit very many human targets.” Ocean State Tactical, LLC v. Rhode Island, 95 F.4th 38, 49 (1st Cir. 2024), cert. denied, 145 S. Ct. 2771 (2025). For example, a 30-round magazine can be emptied in as little as five seconds. See Kolbe, 849 F.3d at 125.

Because LCMs can enable shooters of assault weap ons to fire even more rounds before pausing to reload, they reduce or eliminate the crucial windows that would otherwise “afford intended victims and law enforcement officers a precious opportunity to flee, take cover, and fight back.” Duncan v. Bonta, 133 F.4th 852, 877–878 (9th

63 The Cook County Ordinance at issue in Viramontes, No. 25-238, and the Connecticut law at issue in Grant, No. 25-566, restrict a cate gory of assault weapons defined in part by their compatibility with detachable magazines. See Cook County, Ill., Code of Ordinances §§ 54-211, 54-212(a); Conn. Gen. Stat. § 53-202a. While the question presented concerns the constitutionality of assault-weapons re strictions specifically, legislatures—including Cook County’s—often treat assault weapons and large-capacity magazines as a single, inte grated danger: in many cases, an assault weapon achieves its distinc tive lethality precisely because it is built to accept such a magazine. Accordingly, where this brief discusses large-capacity magazines, it does so to illuminate what makes assault weapons distinctively dan gerous.

Cir. 2025) (en banc). While this sustained capacity serves no ordinary self-defense purpose,64 it renders firearms used in mass shootings exceedingly more dangerous.

Firsthand accounts of recent mass shootings illus trate the danger of eliminating the reload window. In Newtown, nine children fled and two were able to hide during the shooter’s reload. See Or. Firearms Fed’n v. Kotek, 682 F. Supp. 3d 874, 898 (D. Or. 2023). During the 2011 Tucson, Arizona shooting that killed six and injured others, including Representative Gabrielle Giffords, he roic bystanders were able to interrupt the attack when the shooter paused to reload.65 Without those critical few sec onds in Newtown and Tucson, many more could have been killed.

Given these design features, it is no surprise that assault weapons are disproportionately used in the coun try’s deadliest shootings. Even according to the gun in dustry’s own numbers, AR-15-style rifles account for only about 5% of the firearms in the United States, but they have been used in roughly 25% of mass shootings. See Bianchi, 111 F.4th at 455–456. And the disparity grows as mass shootings become more deadly: assault weapons are “used in about 50% of mass shootings with six or more deaths,” and “80[%] of all mass shootings that resulted in more than 24 deaths.” Rupp v. Bonta, 723 F. Supp. 3d 837, 853–854 (C.D. Cal. 2024). “Semiautomatic firearms fitted with LCMs are highly effective weapons of mass slaughter.” Ocean State Tactical, 95 F.4th at 46.

64 Bianchi, 111 F.4th at 459 (pointing to “one study finding that when citizens fire shots in self-defense, they fire an average of two shots and, 97% of the time, fire five shots or fewer”); Ocean State Tactical, 95 F.4th at 49 (explaining that “empirically this is not a useful feature for self-defense”).

65 See Jessica Hopper et al., Heroes of Tucson Shooting: “Something Had to Be Done,” ABC News (Jan. 10, 2011), https://perma.cc/7PA3- ETUS.

In a case from 2019, the First Circuit noted that “AR 15s equipped with LCMs have been the weapons of choice in many of the deadliest mass shootings in recent history, including horrific events in Pittsburgh (2018), Parkland (2018), Las Vegas (2017), Sutherland Springs (2017), Or lando (2016), Newtown (2012), and Aurora (2012).” Worman v. Healey, 922 F.3d 26, 39 (1st Cir. 2019), abro gated on other grounds by Bruen, 597 U.S. 1. In the years since, the awful trend has continued: El Paso, Texas (2019; twenty-three killed, twenty-two more wounded); Buffalo, New York (2022; ten killed, three more wounded); Uvalde, Texas (2022; twenty-one killed, seven teen more wounded); and Highland Park, Illinois (2022; seven killed, forty-eight more wounded) can all be added to the list.66 Even that list is not exhaustive; Respondent’s Brief in Opposition (at 3–4) catalogs nine more mass shootings involving assault weapons in just the year and a half since judgment was entered in this case. Since 2016,

66 See Kayla McCormick & Phil Helsel, El Paso Walmart Mass Shooter Patrick Crusius Sentenced to 90 Consecutive Life Terms, NBC News (July 7, 2023), https://nbcnews.to/4i8zNxz; What We Know About the El Paso and Dayton Shooters’ Guns, PBS News

Hour (Aug. 6, 2019), https://perma.cc/3WGB-9DR9; Aaron C. Davis & Jon Swaine, Suspect in Buffalo Shooting Modified Bushmaster So It Could Hold More Ammunition, Wash. Post (May 15, 2022), https://bit.ly/4jDgaPr; Reese Oxner, Uvalde Gunman Legally Bought AR Rifles Days Before Shooting, Law Enforcement Says, Tex. Trib. (May 25, 2022), https://perma.cc/67TH-LNHT; Frank Main, Illinois State Police director defends decision to give suspected Highland Park killer a gun permit in 2020, Chi. Sun-Times (July 6, 2022), https://perma.cc/LX5X-5GEQ; Julia Jacobo & Nadine El

Bawab, Timeline: How the Shooting at a Texas Elementary School Unfolded, ABC News (updated Dec. 12, 2022), https://perma.cc/ 9KJX-YPP5.

all 10 of the highest-casualty mass shootings have in volved an assault weapon.67

Assault weapons are not only disproportionately rep resented in mass shootings; they also cause dispropor tionately more harm than other firearms. A typical AR 15 round travels at roughly 3,000 feet per second, “three

times the velocity of a typical handgun,” Bianchi, 111 F.4th at 454 (quoting Rupp, 723 F. Supp. 3d at 853), and when the bullet “impacts human tissue,” it creates a wound cavity “up to 11 to 12.5 times larger than the bullet itself,” ibid. (quoting Del. State Sportsmen’s Ass’n v. Del. Dep’t of Safety & Homeland Sec., 664 F. Supp. 3d 584, 599 (D. Del. 2023)). Whereas a typical handgun results in a wound “of one to two inches,” a wound from an AR-15 “will literally pulverize the liver, perhaps best described as dropping a watermelon onto concrete.” Bianchi, 111 F.4th at 454 (quoting Capen v. Campbell, No. 22-cv-11431, 2023 WL 8851005, at *15 (D. Mass. Dec. 21, 2023)).

The resulting harm is measurable at the incident level: Research shows that mass shootings are more than 60% deadlier when an assault rifle is used—12.9 fatalities per shooting, compared to 7.8. See Rupp, 723 F. Supp. 3d at 854. Mass shootings involving an assault weapon or LCM result in roughly four times as many people shot, two times as many killed, and more than thirteen times as many nonfatally injured as incidents involving neither.68

Empirical research confirms that laws regulating assault weapons work: states and localities that regulate them experience fewer and less lethal mass shootings than those that do not. A 2015 study examining both state and federal assault-weapon safety laws from 1982 to 2011

67 Tannuja D. Rozario & Paige Tetens, Everytown Rsch. & Pol’y, As sault Weapons and High-Capacity Magazines (Mar. 19, 2019, last updated June 24, 2026), https://perma.cc/NJ6V-JSB5. 68 Rozario & Tetens, supra note 67.

found that each had “statistically significant and negative effects on mass shooting fatalities.”69 A more recent study reached the same conclusion with newer data: examining mass-shooting incidents across the United States from 2014 to 2022, the study found that counties in states with an assault-weapons law were associated with a 41% lower incidence of mass-shooting fatalities than counties with out one.70

The federal government’s own experience is illus trative. During the decade that the federal law on assault weapons was in place, mass-shooting fatalities were 70% less likely to occur than in the years before or after.71

Other studies have estimated how many mass shoot ings the federal law prevented. One statistical analysis of shooting data from 1966 to 2019 found that the federal law prevented an estimated eleven public mass shootings dur ing the decade it was in force, and if it had continued through 2019, it would have prevented an estimated thirty more.72 Another study reached a similar conclusion, esti mating continuing the federal law through 2022 would

69 Mark Gius, The Impact of State and Federal Assault Weapons Bans on Public Mass Shootings, 22 Applied Econ. Letters 281, 281 (2015).

70 See Charles J. DiMaggio et al., State Assault Weapons Bans Are Associated with Fewer Fatalities: Analysis of US County Mass Shooting Incidents (2014–2022), 32 Injury Prevention 317, 317 (2026). 71 See Charles DiMaggio et al., Changes in US Mass Shooting Deaths Associated with the 1994–2004 Federal Assault Weapons Ban: Anal

ysis of Open-Source Data, 86 J. Trauma & Acute Care Surgery 11, 11 (2019).

72 See Lori Post et al., Impact of Firearm Surveillance on Gun Con trol Policy: Regression Discontinuity Analysis, 7 JMIR Pub. Health Surveill. e26042, e26042 (2021).

have prevented as many as thirty-eight more mass shoot ings.73

States have adopted a range of firearm measures to promote the safety and well-being of residents 1. In recognition of the unique harm posed by assault weapons, both states and the federal government have long imposed public safety measures that limit those par ticularly lethal weapons—frequently in direct response to mass-casualty shootings. Doing so is well within states’ longstanding constitutional prerogative to exercise their traditional police power to protect the health, safety, and welfare of their residents. See Gonzales v. Oregon, 546 U.S. 243, 270 (2006) (recognizing states’ “great latitude under their police powers to legislate as to the protection of the lives, limbs, health, comfort, and quiet of all per sons”).

As respondents’ briefs explain, assault-weapon laws have a deep historical pedigree. See Cook County Resp. Br. at 15–25; Higgins Resp. Br. at 9–23; see also Bianchi, 111 F.4th at 464 (“[L]egislatures, since the time of our founding, have responded to the most urgent and visible threats posed by excessively harmful arms with respon sive and proportional legislation.”). The Governors Safer Communities Initiative highlights a non-exhaustive sur

vey of relevant safety measures here to underscore that these laws reflect the considered judgment of the chief ex ecutives who bear ultimate responsibility for public safety of their residents, often exercised in the immediate after math of tragedy.

In 1989, California passed an assault-weapons law after a shooter killed five children and wounded thirty-one

73 See Alex Lars Lundberg et al., Public Mass Shootings: Counter factual Trend Analysis of the Federal Assault Weapons Ban, 10 JMIR Pub. Health Surveillance e62952, e62952 (2024).

others during recess at a Stockton elementary school, us ing an AK-47-style rifle and magazines holding up to sev enty-five rounds.74 Less than five months later, Republi can Governor George Deukmejian signed California’s

state law.75 The federal law followed California’s example: from 1994 to 2004, Congress prohibited the manufacture, transfer, and possession of assault weapons nationwide (with some exceptions). See Public Safety and Recrea

tional Firearms Use Protection Act, Pub. L. No. 103-322, tit. XI, subtit. A, §§ 110101–110106, 108 Stat. 1796, 1996– 2000 (1994).

Since that time, many other states have followed suit. Connecticut first passed an assault-weapons law in 1993, but substantially expanded that law in 2013—months af ter the Sandy Hook Elementary School shooting in New town that killed twenty-six people, including twenty chil dren—and again in 2023.76 The shooter used three weap ons, one of them an assault rifle.77

Two other states, New York and Maryland, quickly passed laws in response to the Sandy Hook shooting. New York’s SAFE Act, signed by Governor Andrew Cuomo in January 2013, broadened the State’s pre-existing assault

74 See Cal. Penal Code §§ 30500–30515, 30600, 30605; Elizabeth Ire land & Josh Susong, In Stockton, an Earlier Mass Shooting Brought a Monumental Shift in State Law, Stocktonia (Nov. 30, 2025), https://perma.cc/7PHL-JSDK.

75 See Ireland & Susong, supra note 74.

76 Conn. Gen. Stat. §§ 53-202b, 53-202c, 53-202d, 53-202w(b); Mark Memmott, “Historic” Gun Bill Becomes Law in Connecticut, NPR (Apr. 4, 2013), https://n.pr/3TXFkxR; Nat’l Ass’n for Gun Rts. v. La mont, 153 F.4th 213, 223 (2d Cir. 2025) (describing history of Con necticut’s safety measures), cert. granted sub nom. Grant v. Higgins, 146 S. Ct. 2811 (2026).

77 Steve Almasy, Newtown Shooter’s Guns: What We Know, CNN (Dec. 19, 2012), https://cnn.it/4iJo3Rp.

weapons law.78 Maryland’s Firearm Safety Act, also a di rect legislative response to Sandy Hook, followed several months later, regulating assault weapons under Governor Martin O’Malley.79

Subsequent mass-casualty events spurred additional state action. In 2022, within a span of less than two weeks, assault rifles were used to kill twenty-one people (nine teen children) at a Uvalde, Texas elementary school and ten people in Buffalo, at Tops grocery store.80 Weeks later, in response, Delaware enacted an assault-weapons law.81

Illinois Representative Bob Morgan was present at the 2022 Highland Park July 4th parade shooting, where seven people were killed and nearly fifty more wounded by a shooter using an assault weapon fed by three 30- round magazines.82 He co-sponsored the state’s Protect Il

78 N.Y. Penal Law §§ 265.00(22), 265.02(7)–(8); Joel Rose, New York the First State to Pass Gun Control Measures After Newtown Shoot ings, NPR (Jan. 15, 2013), https://n.pr/4zPDYUT.

79 Md. Code Ann., Crim. Law §§ 4-301(d), 4-303(a), 4-305(b); Lacey Johnson, Maryland Governor Signs Tough Gun Control Law, Reu ters (May 16, 2013), https://perma.cc/3YY7-SWGJ.

80 Zach Despart, “He Has a Battle Rifle”: Police Feared Uvalde Gun man’s AR-15, Tex. Trib. (Mar. 20, 2023), https://perma.cc/E4MA E9G8; Press Release, U.S. Dep’t of Just., Federal Grand Jury In dicts Accused Tops Shooter on Federal Hate Crimes and Firearms

Charges in Buffalo, New York (July 14, 2022), https://perma.cc/ YXP7-3B3U.

81 Del. Code Ann. tit. 11, §§ 1465, 1466(a), 1468, 1469(a); Del. Gov. Newsroom, Members of the General Assembly Announce Gun Safety Package (June 2, 2022), https://perma.cc/BUR5-FJJW. 82 Amanda Vinicky, Local Legislators Spent Years Trying to Pass Gun Laws. After Highland Park’s Deadly Parade Shooting, Illinois Took Action, WTTW News (July 3, 2023), https://perma.cc/7AR7- HKNB; Robert Crimo III indicted on 117 counts in deadly Highland

linois Communities Act, which regulated the sale of as sault weapons, signed by Governor Pritzker roughly six months later.83

Legislative action in other states, both the success ful and the not-yet-successful, shows that enacting these crucial safety measures can take time.

Washington’s law on assault weapons traces back to a 2016 mass shooting at a house party in Mukilteo where the shooter used an assault weapon to kill three people; then-Attorney General (now Governor) Bob Ferguson first proposed an assault-weapons bill the following year and reintroduced it annually until it passed in 2023.84 Rhode Island and Virginia, the most recent jurisdictions to enact laws regulating assault weapons, both took years of repeated failed attempts before passing laws in 2025 and 2026, respectively.85

Park parade shooting, prosecutors say, ABC7 Chicago (July 27, 2022), https://perma.cc/38YL-NCU4.

83 720 Ill. Comp. Stat. Ann. 5/24-1.9, 5/24-1.10; Protect Illinois Com munities Act, Pub. Act 102-1116 (Ill. 2023); H.B. 5471, 102nd Gen. As semb. (Ill. 2022), https://legiscan.com/IL/sponsors/HB5471/2021. 84 Wash. Rev. Code § 9.41.390; Alanna Mayham, Washington Gover nor Signs Assault Weapon Sales Ban, Courthouse News Serv. (Apr. 25, 2023), https://perma.cc/5ZH5-WSKV; Press Release, Wash. State Off. of the Att’y Gen., Gov. Inslee Legislation Banning Sale of As sault Weapons Passes House in Historic Vote This Evening (Mar. 8, 2023), https://perma.cc/9M83-3G9V.

85 See R.I. Gen. Laws §§ 11-47.2-1 to -3 (2026); Act of June 26, 2025, ch. 281, 2025 R.I. Pub. Laws (S. 359, Substitute A); Va. Code Ann. § 18.2-287.4:1(B); Act of May 14, 2026, ch. 1106, 2026 Va. Acts (H.B. 217/S.B. 749); Kimberlee Kruesi, Rhode Island’s Assault Weapon Ban Offers a Peek into Why Such Laws Are Difficult to Pass, NBC Bos. (July 5, 2025), https://perma.cc/FPY4-8LV5 (noting that passing the law “took Rhode Island lawmakers more than 10 years”); Jared Serre, Assault Weapons Ban Could Have New Path Forward Under Gov. Spanberger, Lawmakers Say, ARLnow (Jan. 12, 2026), https:// perma.cc/AN56-8XUF (noting the ban passed both chambers in the

Minnesota’s recent experience shows this dynamic still playing out. On August 27, 2025, a gunman fired more than 120 rounds through the windows of Annunciation Catholic Church and School in Minneapolis, killing two children and wounding twenty-one others, most of them children.86 The shooter used an assault rifle, along with a shotgun and pistol.87 Governor Walz pushed for a special session, and the state Senate later narrowly passed a bill to regulate assault weapons, but the resulting bill did not pass in the 2026 session.88

Together, these accounts demonstrate that the ques tion whether and how to regulate assault weapons re mains a live one in state legislatures across the country— being debated and refined in real time. That ongoing pro cess is precisely what our federal structure was and is de signed to protect. From the founding, states have re tained broad authority under their police power to legis late for the safety of their residents, see Gonzales, 546 U.S. at 270, and our federalist system depends on the

states’ freedom to serve as “laborator[ies]” designed to

two preceding legislative sessions, but was vetoed each time by Gov ernor Youngkin before finally being signed into law in 2026). 86 Aki Nace et al., Minneapolis Catholic School Shooting Leaves 2 Children Dead, 21 People Injured, CBS News Minn. (Aug. 27, 2025), https://perma.cc/3D5X-L78U.

87 Deena Winter & Paul Walsh, Suspected Shooter Legally Purchased Rifle, Pistol and Shotgun; Local Politicians Call for Action, Star Trib. (Aug. 28, 2025), https://bit.ly/4yVY4w8.

88 Corin Hoggard, Gov. Walz Bypasses Special Session, Issues Exec utive Orders on Gun Control, Fox 9 Minneapolis-St. Paul (Dec. 16, 2025), https://bit.ly/4jBXnE6; Esme Murphy & Ubah Ali, Minnesota Bill That Would Regulate Ownership, Sale of Semiautomatic Weap ons Passes Senate, CBS News Minn. (May 4, 2026), https://perma.cc/ 3ZUV-ZCF2; S.F. 4067, 94th Leg., Reg. Sess. (Minn. 2026) (passed Senate, not enacted); Aki Nace, Minnesota Legislative Session Ends with No House Vote on Gun Reform Bill, CBS News Minn. (May 18, 2026), https://perma.cc/B9FH-UUMB.

“try novel social and economic experiments without risk to the rest of the country,” New State Ice Co. v. Lieb mann, 285 U.S. 262, 311 (1932) (Brandeis, J., dissenting).

A ruling foreclosing this category of public safety laws would undermine the constitutional balance of feder alism by cutting off the ongoing political process in the states, like Minnesota, still working through it. This Court should “honor the worthy virtues of federalism and democracy, not . . . stifle them.” Bianchi, 111 F.4th at 447. To do otherwise “would unduly impede the workings of legislative bodies across our country as they struggle to meet the challenges of today and tomorrow.” Ibid.

CONCLUSION

In the wake of assault-weapon mass shootings, mem bers of the Governors Safer Communities Initiative have stood with grieving families, exhausted first responders, and community members working to rebuild. The safety of our residents is our obligation, and it is at stake. The judgments of the courts of appeals should be affirmed.

Respectfully submitted.

STEPHEN K. WIRTH

Counsel of Record

JACOBSON LAWYERS

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OCTOBER 28, 2026

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Posted in Assault Weapons Restrictions, Delaware's Office of Gun Prevention and Community Safety, Governor Matt Meyer, assault weapons, brief with the U.S. Supreme Court, gun safety measures, state and local laws

Governor Meyer Joins Multi-State Brief on Assault Weapons Restrictions

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