The Trump Department of Justice has opened a two-front legal assault on Colorado’s gun restrictions, filing United States v. City and County of Denver on May 5, 2026, challenging Denver’s assault weapon ordinance, and following the very next day with United States v. State of Colorado, No. 1:26-cv-01950 (D. Colo.), targeting the state’s large-capacity magazine ban. Both cases land in the Tenth Circuit. They are significant on their own terms — but the Colorado complaint contains something more: a legal maneuver years in the making that is going to cause Colorado serious problems.
Colorado Gets Hoisted on Its Own Petard
The headline from the Colorado magazine-ban complaint is not the legal theory — it’s the ammunition. Back in the early 2010s, when Colorado’s magazine ban was first challenged in Colorado Outfitters Ass’n v. Hickenlooper, 823 F.3d 537 (10th Cir. 2016), and in the parallel state litigation that ultimately reached the Colorado Supreme Court as Rocky Mountain Gun Owners v. Hickenlooper (later v. Polis), 2020 CO 66, Colorado entered into a set of binding factual stipulations. At the time, those cases were not winners for our side. But the factual record Colorado agreed to? That record just came back around.
Paragraphs 27 through 32 of the 2026 federal complaint quote those stipulations directly. Colorado agreed that more than 300 million firearms are lawfully owned in the United States. It agreed that a significant percentage of privately owned firearms are semi-automatic, most of which use a detachable box magazine of the type the state now bans. It agreed that the number of lawfully owned semi-automatic firearms in the U.S. that use such magazines is in the tens of millions. It agreed that several million AR-15 platform rifles have been lawfully purchased and are used for lawful purposes. And it agreed that in states without magazine restrictions, AR-15s are typically sold at retail with 30-round magazines, with a majority of owners using 20- and/or 30-round magazines.
Colorado conceded all of that. Years ago. On the record. And now the Trump administration is using those admissions to argue that magazines capable of holding more than 15 rounds — the kind Colorado bans — are in common use for lawful purposes by law-abiding Americans. Under District of Columbia v. Heller, 554 U.S. 570 (2008), and New York State Rifle & Pistol Ass’n v. Bruen, 597 U.S. 1 (2022), that is essentially the ballgame. This is what I mean when I say brick by brick. That stipulation felt like a minor procedural footnote years ago. Today it may be the most important document in the case.
The Denver Complaint and Justice Thomas’s Words
The Denver complaint goes after the city’s ordinance under Denver Revised Municipal Code § 38-121(c), which makes it a crime to carry, store, keep, manufacture, sell, or otherwise possess an “assault weapon.” The DOJ complaint correctly notes — citing Justice Thomas — that “assault weapon” is a rhetorically charged political term developed by anti-gun publicists, not a technical designation from the firearms industry. What Denver’s ordinance actually bans are ordinary semi-automatic rifles possessed by tens of millions of law-abiding Americans.
To drive the common-use point home, the Denver complaint pulls a line directly from Smith & Wesson Brands, Inc. v. Estados Unidos Mexicanos, No. 23-1141 (U.S. June 5, 2025), the 9–0 opinion authored by Justice Kagan: “The AR-15 is the most popular rifle in the country.” When even a unanimous Supreme Court — writing through its most liberal member — acknowledges that as settled fact, the burden on Denver to show the AR-15 is dangerous and unusual becomes effectively impossible to carry.
Harmeet Dhillon, who directs the DOJ Civil Rights Division that houses the Second Amendment Section, captured the stakes on X:
“I’m truly grateful for the vision and leadership of President Trump, former Attorney General Bondi, and Deputy Attorney General Todd Blanche, the acting attorney general, in enabling our team to stand up in court again and again for the rights of all law-abiding Americans to fully enjoy their cherished Second Amendment rights.”
She also stated plainly that “Colorado’s ban on certain magazines is political virtue signaling at the expense of Americans’ constitutional right to keep and bear arms.”
Personnel Is Policy — and Policy Is Starting to Win
Both complaints were signed by Barry Arrington, Acting Chief of the Second Amendment Section. Arrington spent years as Chief Legal Counsel for Rocky Mountain Gun Owners — the same organization that was a plaintiff in the very Colorado litigation whose stipulations the DOJ is now wielding. He is a Colorado-based lawyer, not a beltway hire. That is not a coincidence.
This is the “outside the beltway” hiring strategy I have been talking about for over a year. The last thing the Second Amendment Section needs is attorneys drawn exclusively from the D.C. professional class. Allowing DOJ lawyers to work out of local U.S. Attorney offices means recruiting talent where Second Amendment experience actually lives. In Arrington’s case, that local knowledge is not just a resume line — it is a direct strategic asset embedded in the complaint itself.
The 10th Circuit Is Squishy — But That’s Not the Real Audience
I will be honest: the Tenth Circuit is not a sure thing on Second Amendment issues. It has been inconsistent post-Bruen, and I would not describe it as reliably friendly territory. But that is not the only reason these cases matter.
Chief Justice Roberts was Principal Deputy Solicitor General. Justice Alito was an Assistant to the Solicitor General. Justice Kavanaugh worked closely with the White House Counsel. These Justices take seriously what the Department of Justice argues before the federal courts. When the federal government itself files complaints saying AR-15 bans and magazine restrictions violate the Second Amendment, that sends a signal SCOTUS cannot ignore.
My mild concern is alignment at the Solicitor General’s office. D. John Sauer and Sarah Harris are the ones who argue before SCOTUS, and I want to make sure they are fully coordinated with what the Second Amendment Section is building here. I have not been happy about Sauer’s decision to petition the Court in United States v. Hemani, the 18 U.S.C. § 922(g)(3) cannabis case — that was a strategic misstep in my view. But the good news is that Acting Attorney General Todd Blanche sits above Sauer in the chain of command. If there is a disagreement about Supreme Court strategy, Blanche has the final word.
The stipulations are locked in. The cases are filed. The right lawyers are signing the complaints. Now we watch.
This article is based on analysis by Professor Mark W. Smith, constitutional attorney and Host of the Four Boxes Diner 2nd Amendment channel. Watch the original video here. This does not constitute legal advice.