Colorado has limited ammunition magazines to 15 rounds since 2013. Now the U.S. Department of Justice is in court arguing that Colorado’s “large-capacity magazine” law is not just bad policy, but unconstitutional.
That lawsuit tees up a question that sounds simple until you touch the Constitution: who controls gun policy in America, states or the federal government?
The answer is both. And whichever side you want to “win” tends to depend on which part of the Constitution you read first.
Join the Discussion
What Colorado banned, and what the DOJ is challenging
Colorado’s law, enacted in 2013 and signed by then-Governor John Hickenlooper, prohibits magazines that hold more than 15 rounds.
The Justice Department’s legal theory is straightforward: magazines of the type Colorado restrict are not exotic accessories, but what the DOJ calls “standard capacity” magazines. In its public statement announcing the lawsuit, the Department said it is “alleging that the State [Colorado] unconstitutionally bans certain constitutionally protected standard capacity firearm magazines” and that the law “unconstitutionally infringes on the Second Amendment rights of law-abiding citizens to keep and bear arms in common use for lawful purposes.”
Assistant Attorney General Harmeet Dhillon, who leads the Civil Rights Division, put the point in political as well as constitutional terms: “Colorado’s ban on certain magazines is political virtue signaling at the expense of Americans’ constitutional right to keep and bear arms.”
A broader push, not a one-off case
The Colorado magazine case is not happening in isolation. The DOJ also filed a lawsuit Tuesday against Denver’s “assault weapons” ban, with Acting Attorney General Todd Blanche saying the ban “directly violates the right to bear arms.”
Together, the two filings underline the posture the federal government is taking here: this is not pitched as a policy disagreement with local lawmakers, but as a rights-based challenge meant to test the constitutional boundaries of state and city gun restrictions.
States write most gun rules, until the Constitution says they cannot
In everyday life, it feels like states run the show on guns because they do much of the regulating. States set licensing systems, define prohibited places, regulate carrying methods, and write criminal penalties. That is not an accident. Under our federal system, states retain what lawyers call the “police power,” meaning broad authority to legislate for public safety.
But there is a hard ceiling on that power: the U.S. Constitution.
The Supremacy Clause makes federal law the “supreme Law of the Land.” Yet the bigger constraint here is not a federal statute. It is the Bill of Rights as applied to the states through the Fourteenth Amendment. Once the Second Amendment is in play, the question becomes less about whether Colorado can regulate firearms generally, and more about whether this particular restriction crosses the line the Constitution draws.
The key battleground is the Second Amendment test
For years, gun cases often turned on a balancing act: courts weighed an individual right against government interests like reducing crime. That approach has largely been displaced by the Supreme Court’s modern framework, which asks whether a challenged gun regulation is consistent with the nation’s historical tradition of firearm regulation.
That matters because magazine limits are a modern policy tool. Defenders of these laws typically argue that limiting rounds reduces the harm of mass shootings and forces shooters to reload. Challengers counter that magazines are integral components of commonly owned firearms and that bans on commonly possessed magazines collide with a right that protects arms “in common use” for lawful purposes.
The DOJ’s announcement leans heavily into that “common use” concept, signaling the case will be framed not as a narrow dispute about accessories, but as a broader question: can a state ban a widely possessed piece of firearm equipment and still claim it is regulating, not prohibiting?
States’ rights vs. individual rights
This is where constitutional rhetoric often gets inverted.
People reach for “states’ rights” language when they want local control. But the Bill of Rights exists precisely because local majorities can be tempted to trade liberty for security. The Second Amendment, whatever else you think it means, is written as a limitation on government power. Once incorporated against the states, it becomes a limitation on state power too.
So the core dispute is not whether Colorado is “allowed to care about public safety.” It is whether the state may pursue public safety in this way when the Constitution protects the underlying conduct.
If a court agrees with the DOJ that these magazines are constitutionally protected arms, or essential to arms in common use, then Colorado’s policy preference does not matter. If a court finds a historical analogue supporting such limits, or concludes the law regulates without substantially burdening protected conduct, then Colorado’s ban survives even if federal officials dislike it.
Why the federal government is involved
A common misconception is that the federal government can only step into a state law fight if Congress has passed a statute preempting state law. That is one pathway, but it is not the only one.
Here, the Justice Department is positioning itself as a constitutional enforcer. That approach treats the Second Amendment less like a policy dispute and more like a civil rights boundary. The DOJ’s own framing reinforces that point by routing the effort through the Civil Rights Division and explicitly describing the contested magazines as “constitutionally protected.”
In other words, the federal government is not saying, “we have a better gun law.” It is saying, “you crossed a constitutional line.”
What a ruling could do, and what it cannot
Even if the DOJ wins, this lawsuit would not automatically nationalize gun policy. Courts do not write comprehensive gun codes. They decide whether a specific law violates the Constitution.
- If Colorado loses, the most direct outcome would be an injunction preventing enforcement of the 15-round limit, at least within the jurisdiction of the deciding court.
- If Colorado wins, states with similar laws are likely to cite that decision to defend their own restrictions, while challengers look for a different case to take up the issue again.
Either way, the larger consequence is doctrinal. Magazine bans have become a proxy fight over how strictly courts will apply the “history and tradition” approach and how expansively they will interpret “common use.” And paired with challenges like the DOJ’s lawsuit against Denver’s “assault weapons” ban, the courts may be pushed to clarify not only what kinds of weapons are protected, but what kinds of parts and configurations fall inside the Second Amendment’s protection.
The federalism lesson
Our system is designed to let states experiment. That is the promise of federalism. But rights are designed to stop certain experiments from happening at all. That is the point of a constitutional floor.
The question “who controls gun policy” therefore has a constitutional answer, not a partisan one:
- States control gun policy within the boundaries of the Second and Fourteenth Amendments.
- The federal government can challenge state and local laws when it believes those laws cross those boundaries.
- Ultimately, the judiciary decides where the boundary sits.
Colorado’s magazine limit is not just a local rule. It is a test case for what it means to say that the Second Amendment is a right, not a suggestion.
