Last updated October 2026 · By Nick Hall, who has followed the AR-15 cases from the cert grant to the merits briefs and read this multistate brief, appendix and signature pages included
Quick take: Massachusetts and New Jersey, joined by 16 other states and the District of Columbia, filed a brief on October 28 telling the Supreme Court that AR-15 bans are constitutional. It is an amicus brief, so it decides nothing, but it is the states’ whole case against the common use test in one place.
- What happened: Eighteen states and DC filed an amicus brief backing Cook County and Connecticut in Viramontes v. Cook County (No. 25-238) and Grant v. Higgins (No. 25-566).
- Why it matters: The brief asks the Court to reject the “common use” test outright, even if the justices end up striking the two bans.
- What’s next: The Court hears one hour of argument in the consolidated cases on Wednesday, December 2, 2026.
- Who to watch: New Jersey, which co-leads this brief while its own AR-15 ban survives only on a stayed Third Circuit mandate.
Most amicus briefs in a big Second Amendment case are noise, a few dozen pages of the same argument the parties already made with a different letterhead. This one is different, because it is 19 governments telling the Court how they want to keep the power to ban AR-15s, and the fallback they would settle for. I read all of it so you do not have to.
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Table of Contents
Who Signed the AR-15 Ban Brief, State by State
The brief is titled “Brief of Massachusetts, New Jersey, 16 Other States, and the District of Columbia as Amici Curiae in Support of Respondents,” and it went onto the Supreme Court docket on October 28, 2026. New Jersey Solicitor General Sundeep Iyer is counsel of record, under Attorney General Jennifer Davenport, with Massachusetts Attorney General Andrea Campbell as co-lead.
Here is the full list from the signature pages: Massachusetts, New Jersey, Arizona, California, Colorado, Delaware, Hawaii, Illinois, Maine, Maryland, Michigan, Minnesota, New Mexico, New York, Oregon, Rhode Island, Vermont and Washington, plus the District of Columbia. Every one of them signed through its attorney general.
Now look at the brief’s own appendix. Table 1 lists the 12 jurisdictions that restrict the possession or sale of assault weapons, and eight of the signers are not on it: Arizona, Colorado, Maine, Michigan, Minnesota, New Mexico, Oregon and Vermont. Those eight are backing a kind of law the brief does not list them as having. Our Arizona gun laws guide covers what that state does restrict.
The states say they filed to explain why “Cook County’s and Connecticut’s regulation of the sale and possession of assault weapons such as the AR-15 within their own borders is wholly consistent with the Second Amendment.” The ask at the end is the standard one: affirm the Second and Seventh Circuits.
The Unusually Dangerous Argument, in Plain English
Part I is a history lesson with a point. The states walk from the 1328 Statute of Northampton and its ban on the launcegay through trap guns, which New Jersey outlawed in 1771, then Bowie knives, slungshots and finally machine guns and the National Firearms Act of 1934.
The claim is that “six circuits have identified a tradition of States regulating weapons that are unusually dangerous,” and that the AR-15 fits that tradition. In the brief’s words, “Under any reasonable understanding of that tradition, assault weapons are disproportionately dangerous compared to their civilian self-defense uses.”
The numbers come mostly from the Seventh Circuit’s Barnett decision. The brief says “only four percent of self-defensive uses involved rifles” in one analysis, and that in a sample of mass shootings with at least 20 deaths from 1991 to 2022, 75% involved assault weapons.
It also cites the Court’s own 2026 decisions in Wolford v. Lopez and United States v. Hemani, and argues that a tradition built from many historical laws should be read more broadly than the single set of laws the Court weighed in those cases. That is the technical heart of the brief.
Why the States Want the Common Use Test Gone
Part II goes after the test the gun owners rely on. The states say it would “reduce the Second Amendment to a mere counting exercise,” and they list five problems with it, from history to what they call an illogical arms race between gun makers and legislatures.
The machine gun point is the sharpest one in the brief. The brief says there are “more than 700,000 machine guns registered with the federal government,” against the 200,000 stun guns that Justice Alito’s Caetano concurrence treated as enough. “Petitioners offer no limiting principle,” it says, for protecting one and not the other. Bump stocks get the same treatment, with an estimated 280,000 to 520,000 in circulation as of 2018.
The arms race argument is aimed at our side of the counter. If popularity buys protection, the states say, the test would “incentivize gun retailers to flood the market with their new items” before a legislature can act, and nothing in history says “governments can regulate firearms only if they get in the game early enough.”
A footnote matters to anyone who owns standard-capacity magazines. The states call bump stocks and magazines constitutionally distinct from the rifles in this case, then add that “Amici may raise separate arguments in future cases concerning bump stocks and LCMs.” That is a marker, and it reads like one.
Nineteen Governments Against the Justice Department
The United States filed its own amicus brief on September 4, in support of the gun owners, and on September 9 the Solicitor General asked for leave to argue and for divided argument time. The states answer it by name, twice, on the history of English weapons laws and on the 19th-century Bowie knife cases, where they say “The United States incorrectly suggests” those courts approved bans because the knives were not in common use.
And the closing paragraph is the line I would underline. “No matter whether this Court affirms the judgments of the Second and Seventh Circuits, it should reject Petitioners’ ahistorical Second Amendment test.” Read that twice and it is a fallback position, written by people who know they might lose the two bans and want to keep the method.
The brief landed the same day as nine other amicus filings on the docket, from Virginia, the International Association of Chiefs of Police, historians, Giffords Law Center, Everytown, groups of teachers and school nurses, the Governors Safer Communities Initiative, the Major Cities Chiefs Association with the US Conference of Mayors, and a group of medical societies led by the American Academy of Pediatrics.
New Jersey’s Own AR-15 Ban Rides on This Case
The co-lead state has the most riding on December. On July 17, 2026, the en banc Third Circuit ruled against New Jersey “on a 10-5 vote,” holding its assault weapons and magazine restrictions unconstitutional. The court then stayed its mandate, and New Jersey’s own cert petition, No. 26-452, says “the LCM and Assault Weapons provisions remain in effect.”
That petition asks the justices to hold New Jersey’s case until they decide Viramontes and Grant, which we covered when New Jersey asked SCOTUS to hold its AR-15 case. So when Davenport’s office argues for Cook County and Connecticut, it is arguing for its own statute by proxy.
For buyers in the 12 Table 1 jurisdictions, nothing changes today. An amicus brief is an argument from a non-party, the bans stay where they are, and the Court has decided nothing.
What Happens Before the December 2 Argument
The Court granted review on June 30, 2026, consolidated the two cases and gave them one hour of argument in total, set for Wednesday, December 2. The question is the one from Cook County’s case: “Whether the Second and Fourteenth Amendments guarantee the right to possess AR-15 platform and similar semiautomatic rifles.”
The parties’ own case is in the Cook County and Connecticut merits briefs, which make the same unusually dangerous argument from the defendants’ chair. This brief is the version with 19 signatures on it. The docket sets no decision date.
Two theories, one question. Popular, or protected.
Frequently Asked Questions
What is an amicus brief at the Supreme Court?
A brief filed by someone who is not a party to the case, offering arguments or information to the justices. It carries no vote and decides nothing. The 18 states and DC in the AR-15 cases are amici, while Cook County, Connecticut and the gun owners are the parties.
Which states signed the brief supporting AR-15 bans?
Massachusetts, New Jersey, Arizona, California, Colorado, Delaware, Hawaii, Illinois, Maine, Maryland, Michigan, Minnesota, New Mexico, New York, Oregon, Rhode Island, Vermont and Washington, plus the District of Columbia. Virginia filed its own separate brief.
What are Viramontes v. Cook County and Grant v. Higgins?
Viramontes (No. 25-238) challenges Cook County, Illinois' assault weapons ordinance and comes from the Seventh Circuit. Grant (No. 25-566) challenges Connecticut's ban and comes from the Second Circuit. The Supreme Court consolidated them on June 30, 2026.
When will the Supreme Court hear the AR-15 ban cases?
Oral argument is set for Wednesday, December 2, 2026, with one hour in total for the two consolidated cases. The docket does not set a decision date.
What is the common use test?
It is the argument, drawn from Heller, that arms in common use by law-abiding citizens for lawful purposes are protected by the Second Amendment. The gun owners say millions of AR-15s meet it. The states call it a counting exercise and ask the Court to reject it.
Does this brief change any gun law right now?
No. Amicus briefs are arguments, and this one changes no statute. The Supreme Court has not ruled, and its eventual decision will speak to the Cook County and Connecticut laws first.
Is New Jersey's AR-15 ban still in effect?
Yes, for now. The en banc Third Circuit ruled against it 10-5 on July 17, 2026, but stayed its mandate, and New Jersey has asked the Supreme Court to hold its petition, No. 26-452, until it decides Viramontes and Grant.
Which side is the federal government on?
The gun owners' side. The United States filed an amicus brief in support of the petitioners on September 4, 2026 and asked for time at oral argument. The states' brief answers the federal brief by name, arguing against its reading of the history.
Related Reading
- Supreme Court Takes the AR-15 Question Head On
- New Jersey’s Assault Weapons Ban Falls: What Changes
- New Jersey Gun Laws
- Massachusetts Gun Laws
- Best AR-15 Rifles
- US Gun Laws by State
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