Gun laws in the United States are both state and federal. Congress sets a nationwide baseline that every gun owner, seller, and buyer must meet, and each state builds its own rules on top of that baseline. The practical result is that two systems apply to you at the same time, and a firearm or accessory that is fully legal in one state can be a crime to possess in the next.
The Federal Floor
Federal firearms law comes primarily from Congress’s power over interstate commerce, and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) is the agency that enforces it.1Bureau of Alcohol, Tobacco, Firearms and Explosives. Gun Control Act of 1968 A handful of statutes do most of the work.
The National Firearms Act of 1934 covers a specific set of weapons: machine guns, short-barreled rifles and shotguns, suppressors, and destructive devices. It doesn’t ban them, but it requires registration in a central federal registry, a background check, and historically a tax.2Congressional Research Service. The National Firearms Act and PL 119-21 – Issues for Congress
The Gun Control Act of 1968 is the broader framework. It requires anyone in the business of selling firearms to hold a federal firearms license (FFL), sets the federal minimum purchase ages at 21 for a handgun and 18 for a rifle or shotgun from a licensed dealer, and lists the people who cannot buy or possess a firearm at all.3Office of the Law Revision Counsel. United States Code Title 18 – Section 922 Unlawful Acts That prohibited-persons list is longer than most people assume. It includes convicted felons, people convicted of misdemeanor domestic violence, people subject to certain domestic violence restraining orders, those who have been involuntarily committed to a mental institution, unlawful users of controlled substances, fugitives from justice, people who have renounced U.S. citizenship, and those in the country illegally.
The Brady Handgun Violence Prevention Act of 1993 built the background check most buyers experience. A licensed dealer must run every buyer through the National Instant Criminal Background Check System (NICS) before completing a transfer, either through the FBI’s NICS Operations Center or a state point of contact.4Bureau of Alcohol, Tobacco, Firearms and Explosives. Brady Permit Chart5eCFR. 28 CFR 25.6 – Accessing Records in the System There is a gap here that catches people off guard: federal law only requires the check when a licensed dealer is involved. A sale between two private individuals who aren’t in the business has no federal background check requirement. Roughly half the states have closed that gap with their own laws; the rest have not.
Buying a gun for someone who is prohibited from buying one themselves is a straw purchase, and it carries its own federal statute with penalties up to 15 years in prison and a $250,000 fine. If the firearm is later used in a felony, a drug trafficking crime, or an act of terrorism, the maximum climbs to 25 years.6Office of the Law Revision Counsel. United States Code Title 18 – Section 932 Straw Purchasing of Firearms
The most recent major federal law is the Bipartisan Safer Communities Act of 2022. It created an enhanced background check for buyers under 21 that can extend the review up to ten business days to allow searches of juvenile and mental health records, expanded the domestic violence misdemeanor prohibitor to include dating partners, and funded state crisis intervention programs.3Office of the Law Revision Counsel. United States Code Title 18 – Section 922 Unlawful Acts7Congress.gov. Text – 117th Congress (2021-2022) Bipartisan Safer Communities Act
What States Add on Top
State legislatures regulate firearms under their general police powers, and they use that authority very differently. The same categories of law exist in many states, but the details swing widely.
Carrying in Public
Concealed carry is where state-to-state variation is starkest. Roughly 29 states now allow permitless carry, meaning any adult who can legally possess a firearm can carry one concealed with no permit required. A smaller group maintains restrictive permitting systems. Most states sit in the middle, issuing permits to anyone who meets objective criteria such as a background check and a training course. States still set training requirements and prohibited locations.
Assault Weapons and Magazine Limits
Several states ban or restrict semi-automatic firearms with certain features, commonly labeled “assault weapons,” and a number of states cap magazine capacity, often at 10 or 15 rounds. Federal law does neither.
Waiting Periods
Some states require a delay of a few days to over a week between purchase and possession. Federal law has no waiting period.
Universal Background Checks
About half the states require background checks on private sales, not just dealer sales. In practice, the buyer and seller go to a licensed dealer, who runs NICS and handles the paperwork for a fee.
Extreme Risk Protection Orders
About 22 states and the District of Columbia have “red flag” laws that let a court temporarily remove firearms from someone found to pose a danger to themselves or others. A family member, household member, or law enforcement officer petitions the court; if the judge agrees, the person surrenders their firearms for a set period, with the right to a hearing.
Safe Storage
About half the states regulate how firearms are stored, particularly in homes with children. Some require guns to be locked or disabled with a trigger lock whenever a minor could access them. Others impose liability only after a child actually gains access to an unsecured firearm. The age cutoff for “child” ranges from 14 to 18 depending on the state.
Ghost Guns
Firearms built from kits or 3D-printed parts without serial numbers are a growing area of state regulation. A number of states now require serial numbers on home-built firearms, ban unserialized frames and receivers, or restrict 3D-printed manufacturing. Federal rules have tightened in this area too, but state laws often reach further.
How the Two Layers Fit Together
The simplest way to think about the relationship: federal law is the floor, not the ceiling.8EveryCRSReport.com. Federal Firearms Laws – Overview and Selected Legal Issues for the 116th Congress States can add restrictions on top, but they cannot drop below the federal minimum. No state can legalize sales to felons, because federal law prohibits them everywhere. But a state can ban a firearm federal law allows, impose a waiting period federal law doesn’t, or require a background check on a sale federal law leaves alone.
You have to comply with both at once. If you buy from a dealer, you clear NICS regardless of your state’s rules. If you live in a state that caps magazines at 10 rounds, a 15-round magazine is a state crime even though federal law permits it.
Enforcement runs on parallel tracks. The ATF enforces federal violations; state and local police enforce state ones. The same conduct can be prosecuted under both systems without triggering double jeopardy, because the federal and state governments are treated as separate sovereigns.
What Changes When You Cross a State Line
Because state laws diverge so sharply, travel is where gun owners get into trouble. A lawfully owned firearm at home can become a criminal charge the moment you cross a border.
Federal Safe Passage
Federal law lets you transport a firearm through a state where possession would otherwise be illegal, as long as you can lawfully possess it at both your origin and your destination. The gun must be unloaded and kept where it isn’t readily accessible from the passenger compartment. In a vehicle without a separate trunk, it must be in a locked container that is not the glove compartment or center console.9Office of the Law Revision Counsel. 18 US Code 926A – Interstate Transportation of Firearms The protection covers transport only. Stop for a night, or do anything beyond passing through, and some states argue the protection lapses. Travelers have been arrested in strict-law states despite invoking safe passage, and the limits remain contested.
Concealed Carry Reciprocity
There is no federal law forcing states to honor each other’s concealed carry permits. States handle recognition individually. Some honor every state’s permit, some honor only permits from states with comparable standards, and a few honor none. These agreements change, and getting it wrong is a criminal matter. Before traveling armed, check the current reciprocity status for every state you’ll enter or pass through, and know that where your permit is honored you’re still bound by the host state’s rules about where and how you can carry.
Flying With a Firearm
Air travel adds a federal layer. TSA requires any firearm in checked baggage to be unloaded, locked in a hard-sided container, and declared at the airline ticket counter.10Transportation Security Administration. Transporting Firearms and Ammunition Firearms are never allowed in carry-on bags. You also still have to comply with the gun laws at your destination, which may be considerably stricter than the laws where you took off.
The Constitutional Backdrop
Both layers sit under the Second Amendment. In District of Columbia v. Heller (2008), the Supreme Court held that the amendment protects an individual right to possess firearms for lawful purposes like self-defense in the home.11Justia Law. District of Columbia v Heller, 554 US 570 (2008) McDonald v. City of Chicago (2010) applied that right against state and local governments.12Justia Law. McDonald v City of Chicago, 561 US 742 (2010) New York State Rifle & Pistol Association v. Bruen (2022) extended the right to carrying firearms in public and announced a new test: a gun regulation covering conduct within the amendment’s text must be consistent with this country’s historical tradition of firearm regulation.13Supreme Court of the United States. New York State Rifle and Pistol Association Inc v Bruen, No 20-843 (2022) United States v. Rahimi (2024) then made clear that someone found by a court to pose a credible threat to another person’s physical safety can be temporarily disarmed without violating the amendment.14Supreme Court of the United States. United States v Rahimi, No 22-915 (2024) The right is real and binds both Congress and the states; it is not unlimited.
Local Rules and State Preemption
Cities and counties can add a third layer, at least in theory. A local ordinance might restrict carrying in parks, limit shooting ranges, or require local registration. That authority flows from the state, and most states have taken it back. Around 45 states have preemption laws that block local governments from writing their own gun rules, reserving the field for the legislature. Some go further and penalize local officials who try to enforce ordinances that conflict with state law. In the few states without strong preemption, city rules can be considerably stricter than the rest of the state, which is one more variation to track for anyone carrying across municipal lines.