In an amicus brief filed on September 4, 2026, for the Viramontes v. Cook County and Grant v. Higgins cases now before the U.S. Supreme Court, the U.S. Department of Justice argued that assault weapons bans are unconstitutional because AR-15s are in “common use” and protected by the Second Amendment, despite their use in the country’s deadliest mass shootings. In its filing, the Trump administration not only sided with the gun lobby to attack commonsense gun safety laws but also echoed many of its same arguments.
The filing is the latest effort by the Trump administration to unravel gun laws and open new markets for deadly weapons, often working hand-in-glove with the gun industry. For example, the Department of Justice has filed lawsuits challenging state bans on assault weapons and high-capacity magazines, settled lawsuits with companies that make AR-15s deadlier, allowed a lapse in National Firearms Act (NFA) enforcement regarding silencers, and announced over 30 rule changes through the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) to deregulate the gun industry.
DOWNPLAYING THE DANGER OF AR-15s
To date, 11 states and Washington, D.C., have enacted laws to prohibit assault weapons. Four out of the five federal courts of appeals that have considered the constitutionality of assault weapon laws since Bruen have upheld them.1Only the Third Circuit has disagreed, finding New Jersey’s assault weapons ban, as to “all covered semi-automatic rifles,” violates the Second Amendment. The Third Circuit then put its ruling on hold pending Supreme Court review.
In its amicus brief, the Department of Justice argues that legislatures cannot prohibit AR-15 rifles under the Second Amendment and even calls into question the “political” term “assault weapon,” with references to it being “developed by anti-gun publicists.” But it was the gun industry itself that began using the term “assault weapon” to market military-style firearms to civilians in 1984.
The Department asserts that the AR-15 is not “especially dangerous.” Instead, it says the AR-15 is “popular” because it is “accurate, light, portable, easy to shoot, easy to accessorize, and configured with components that can be removed and customized.”
There is much debate over how “popular” the AR-15 is; industry research suggests they are highly concentrated among a subset of gun owners who stockpile them. In any event, military-style features make AR-15s and similar assault weapons much deadlier in mass shootings, allowing attackers to fire dozens of shots in rapid succession with greater speed, control, and maneuverability than traditional firearms. Research has found that four times as many people are shot in mass shootings that involve at least one assault weapon or high-capacity magazine than in mass shootings that involve neither. Over the last 10 years, all 10 of the highest-casualty mass shootings have involved both an assault weapon and high-capacity magazines.
The Department barely mentions mass shootings at all, and not until page 29 of its amicus brief. The Department claims that handguns are more dangerous because they’re more often used by criminals and mass shooters, ignoring the reality that a single gunman armed with an AR-15 can kill and injure many more people in seconds, as evidenced by the long list of communities impacted by assault weapons. Both Cook County and Connecticut first banned assault weapons in 1993 — before the federal government did the same the following year — after a rash of high-profile shootings involving such guns. Both also expanded their laws in 2013 after a gunman using a Bushmaster AR-15 to kill 20 young children and seven adults in Newtown.
Since that time, the number of people injured in mass shootings involving AR-15s and other assault weapons has only grown.
Relying on Gun Ownership “Research”
In its amicus brief, the Department of Justice relies in part on flawed research findings as evidence that AR-15s are in “common use” and cannot be prohibited. For example, the Department cited a survey released days before briefs were due by a professor, William English, whose earlier work was criticized for — among other things — having “undisclosed ties to pro-gun interests.” English’s new research claims that roughly a quarter of gun owners own AR-15s. However, the new survey appears to suffer from many of the same flaws as his prior one; it was not peer-reviewed, does not disclose how respondents were recruited, and primes respondents to answer in certain ways.
The Department of Justice also cited figures from the National Shooting Sports Foundation (NSSF), the gun industry’s trade association, estimating that millions of “modern sporting rifles” — a term that the NSSF created for assault weapons like AR-15s — have been produced since 1990. But as discussed here, there is a stark difference between how many assault weapons have been made and how many are currently owned by civilians. The NSSF’s production figures do not distinguish between military, police, or civilian firearms and appear to include those in the hands of prohibited owners, such as criminals and domestic abusers, and those that have been illegally trafficked.
What cannot be argued is that assault weapons have become the weapon of choice for the perpetrators of the country’s most horrific mass shootings. Over 100 million Americans currently live in states that prohibit assault weapons, but those laws are now under attack, and the Trump administration chose to side with the gun lobby’s arguments and perspectives instead of protecting public safety.