Assault weapons are a class of semi-automatic firearms that are designed to kill humans quickly and efficiently.  As the diagram below shows, the military features that clearly distinguish assault weapons from standard sporting firearms enable shooters to spray large amounts of ammunition quickly while retaining control of the weapons.1

Assault weapons have been used in many high-profile shooting incidents, including the 2012 mass shooting at Sandy Hook Elementary School in Newtown, Connecticut, the 2012 Aurora, Colorado movie theater shooting and the 1999 Columbine High School massacre in that state, as well as the 1993 office shooting at the 101 California Street building in San Francisco.2  In fact, a review of 62 mass shootings between 1982 and 2012 by Mother Jones found that assault weapons were recovered in almost a quarter of them.3 A review of mass shootings between January 2009 and January 2013 by Mayors Against Illegal Guns found that incidents where assault weapons or large capacity ammunition magazines were used resulted in 135% more people shot and 57% more killed, compared to other mass shootings.4


In addition, a joint report by scholars in Mexico and the United States found that semi-automatic assault rifles sold in the U.S. are the most sought after and widely used weapons by Mexican drug trafficking organizations.5

A study analyzing FBI data shows that 20% of the law enforcement officers killed in the line of duty from 1998 to 2001 were killed with assault weapons.6 Anecdotal evidence from law enforcement leaders suggests that military-style assault weapons are increasingly being used against law enforcement by drug dealers and gang members.7  In response, law enforcement agencies are upgrading their arsenals to include more assault weapons.8  A 2007 report by the International Association of Chiefs of Police recommended that Congress enact an effective ban on military-style assault weapons in order to curb the ability of criminals to “outgun” law enforcement officers.9

assault_FINALAssault weapons are a relatively new class of firearms. During the 1980s, the firearms industry sought to reverse a decline in consumer demand for guns by developing and marketing new types of weapons based on military designs, including assault weapons.10

Information about the effectiveness of assault weapons bans can be found below.

A strong majority of Americans, including gun owners, consistently support laws prohibiting assault weapons.  For example, a poll conducted in December 2012 found that 62% of Americans favored banning military-style assault weapons.11  In another survey, 67% of Field & Stream readers polled did not consider assault weapons to be legitimate sporting guns.12


Summary of Federal Law

The Lapsed Federal Assault Weapons Ban:  In 1994, Congress adopted the Violent Crime Control and Law Enforcement Act of 1994, which made it “unlawful for a person to manufacture, transfer, or possess” a semiautomatic assault weapon.13  The law was adopted with a sunset clause, however, and expired in 2004, despite overwhelming public support for its renewal.  Thus, semi-automatic, military style weapons that were formerly banned under the federal law are now legal unless banned by state or local law.

The 1994 Act defined the phrase “semiautomatic assault weapon” to include 19 named firearms and copies of those firearms, as well as certain semi-automatic rifles, pistols and shotguns with at least two specified characteristics from a list of features.14  The federal ban also prohibited the transfer and possession of any new  large capacity ammunition magazine.15  Additional information about large capacity ammunition magazines is contained in our summary on Large Capacity Ammunition Magazines.

Despite its limited duration, studies show that the federal assault weapon ban resulted in a marked decrease in the use of assault weapons and large capacity ammunition magazines in crime.  One study found that in several major cities, the share of recovered crime guns that were assault weapons declined by at least 32% after the federal ban was adopted.16  Another study found that the expiration of the federal assault weapon ban likely contributed to increased drug-trafficking related violence in Mexico, which often involves semi-automatic assault rifles sold in the U.S, as noted above. The authors of that study found that after the federal ban expired, there was a 40% increase in homicide rates in areas in Mexico along the Texas, New Mexico and Arizona borders compared to areas along the California border.17 California bans assault weapons under state law while the other border states do not.

The 1994 Act did suffer from notable limitations, however.  The two-feature test and the inclusion of some features that were purely cosmetic in nature created a loophole that allowed manufacturers to successfully circumvent the law by making minor modifications to the weapons they already produced.  The law also did not prohibit the continued transfer or possession of assault weapons manufactured before the law’s effective date.  Manufacturers took advantage of this loophole by boosting production of assault weapons in the months leading up to the ban, creating a legal stockpile of these items.

The Ban on the Importation of Non-Sporting Firearms and Their Parts:  Federal law prohibits any person from importing a firearm unless authorized by the U.S. Attorney General.18  The Attorney General must authorize the importation of any firearm that “is generally recognized as particularly suitable for or readily adaptable to sporting purposes, excluding surplus military firearms.”19 Federal law also prohibits any person from assembling from imported parts any semiautomatic rifle or any shotgun which is identical to any rifle or shotgun prohibited from importation.20

In 1998, ATF announced that semiautomatic rifles capable of accepting large capacity ammunition magazines “are not generally recognized as particularly suitable for or readily adaptable to sporting purposes and are therefore not importable.”21  However, a 2011 report by three U.S. Senators found that, “Since the Clinton Administration’s efforts, the Gun Control Act of 1968’s prohibition against non-sporting firearms has not been aggressively enforced, and many military-style, non-sporting rifles have flowed into the United States civilian market.”22

Summary of State Law

Seven states and the District of Columbia have enacted laws banning assault weapons: California, Connecticut, Hawaii, Maryland, Massachusetts, New Jersey and New York. In addition, Minnesota and Virginia regulate assault weapons.23

Assault weapon bans can be categorized according to: (1) the definition(s) of “assault weapon”; (2) the activities that are prohibited; (3) whether pre-ban weapons are grandfathered; (4) whether grandfathered weapons must be registered; and (5) how transfer and possession of grandfathered weapons are treated.

State Assault Weapons Bans

State List Banned by Name Generic Feature Definition Requires Registration of Grandfathered Weapons Prohibits Transfer of Grandfathered Weapons Limits Places or Requires License
CA24 Yes Yes (One-Feature) Yes Yes Yes
CT25 Yes Yes (One-Feature) Yes Yes Yes
DC26 Yes Yes (One-Feature) N/A 27 N/A N/A
HI (assault pistols only)28 No Yes Yes Yes No
MD29 Yes Yes No30 Yes No
MA31 Yes Yes No No Yes   (license)
NJ32 Yes No 33 Yes No Yes   (license)
NY34 No Yes (One-Feature) Yes Yes No


States that Regulate (But Do Not Ban) Assault Weapons

Description of State Laws Banning Assault Weapons
For additional citations, please see the chart above.

1. Definition: Some state assault weapon bans prohibit specific weapons by listing them by name. Some bans list features that, when present, make a gun an assault weapon. The latter are known as generic feature tests. Generic feature tests, emphasizing high capacity and enhanced control during firing, are intended to identify assault weapons based on the military features that enhance a weapon’s lethality. Generic feature tests that require a weapon to have only one of a list of features are more comprehensive than those that require two. A one-feature test captures more assault weapons and makes it harder for the gun industry to evade the law by modifying banned weapons.

California, Connecticut, New York and the District of Columbia have the most comprehensive approaches to defining assault weapons. California law bans roughly 75 assault weapon types, models and series by name and provides a one-feature generic test for rifles and pistols.37 Connecticut bans roughly 70 assault weapon types, models, and series by name and uses a one-feature generic test for rifles and pistols. The District of Columbia includes a list of assault weapon types, models and series by name that closely follows the California list, and provides a one-feature generic test for rifles, pistols and shotguns.  The District also allows its Chief of Police to designate a firearm as an assault weapon based on a determination that the firearm would pose the same or similar danger to the residents of the District as other assault weapons. New York has adopted a one-feature test for assault pistols, shotguns, and rifles.

New Jersey bans roughly 65 assault weapon types, models and series and copies of those weapons by name and uses a one-feature generic test for shotguns.38 Connecticut and New Jersey also ban parts that may be readily assembled into an assault weapon.

The generic feature tests in other bans, including the expired federal ban, are two-feature tests. Massachusetts use the definition of “assault weapon” from the expired federal law, including both the two-feature test and the federal law’s list of banned weapons.  Hawaii only bans assault pistols, but not assault rifles or shotguns, and uses the two-feature definition from the federal law, but does not include a list of named weapons. Maryland uses its own two-feature test and list of named weapons.

2. Prohibited Activities: Assault weapon bans vary as to which activities are prohibited. California prohibits the broadest range of activities. Both California and Connecticut prohibit possession, distribution, importation, transportation, and keeping or offering for sale of assault weapons.39 In addition, California prohibits the manufacture and transfer of assault weapons, while Connecticut also prohibits giving an assault weapon to another person. New Jersey and New York laws prohibit the manufacture, transportation, sale, shipping, transfer, disposing and possession of assault weapons. Maryland prohibits the possession, sale, offering for sale, transfer, purchase, receipt, or transportation into the state of assault weapons.

3. Grandfathering: Assault weapon bans differ in their treatment of pre-ban weapons. The District of Columbia does not allow the possession of pre-ban weapons. Every state with a ban grandfathers pre-ban weapons. However, California, Connecticut, Hawaii, New Jersey and New York also require registration of such weapons.40 New Jersey’s law is particularly strong because only assault weapons with a legitimate target-shooting purpose may be registered (effectively requiring over 60 models, types and series of assault weapons to be transferred out of state, rendered inoperable, or surrendered to law enforcement). Maryland required registration of grandfathered assault pistols but not assault long guns. See our summary on the Registration of Firearms for further information about registration systems.

California, Connecticut, Hawaii, Maryland, and New York prohibit transfer of all or most grandfathered weapons. Only California and Connecticut limit the places where a grandfathered weapon may be possessed.41 In Massachusetts and New Jersey, grandfathered weapons may only be sold and possessed if the owner has a license. Additional information on licensing of firearm owners is contained in our summary on Licensing Gun Owners & Purchasers.

4. The Takings Clause.  Bans on assault weapons–whether they contain grandfather provisions or not–do not present a problem under the Takings Clause of the Fifth Amendment.

Description of State Regulations Governing Assault Weapons

1. Minnesota: Minnesota prohibits the possession of “semiautomatic military-style assault weapons” by persons under 18 years of age, as well as other prohibited persons, and imposes additional restrictions on transfers through firearms dealers.

2. Virginia: Virginia limits the knowing and intentional possession and transportation of certain semi-automatic “assault firearms” to citizens and permanent residents age 18 and older. These weapons may not be carried, loaded, in public places in certain cities and counties. Virginia also imposes a general ban on the importation, sale, possession and transfer of the “Striker 12” and semi-automatic folding stock shotguns of like kind, but does not refer to them as “assault firearms.”

District of Columbia Tort Liability Law Governing Assault Weapons

The District of Columbia imposes strict tort liability on manufacturers, importers and dealers of assault weapons for all direct and consequential damages that arise from injury or death due to the discharge of an assault weapon in the District (with limited exceptions).42


Cook County, Illinois

Adopted by Cook County, Illinois, in 1993, the Blair Holt Assault Weapons Ban prohibits the manufacture, sale, transfer, or possession of an assault weapon or large capacity magazine in Cook County, Illinois.  The Ban was adopted in 1993, but was amended and renamed in memory of Blair Holt, a 16-year-old boy who was shot and killed as a bystander when gang violence erupted on a bus in 2007.  The law includes an extensive list of prohibited assault weapon types, models and series, and provides a one-feature test identifying other rifles, shotguns, and pistols as assault weapons.  The law defines a large capacity magazine as any ammunition feeding device with the capacity to accept more than ten rounds. The 1993 ordinance enacting this law provided that any person who was legally in possession of an assault weapon or large capacity magazine at that time had 90 days to:  (1) remove it from the County; (2) modify it so it was rendered either inoperable or so changed that it would fall outside the definition of “assault weapon” or “large capacity magazine;” or (3) surrender it to law enforcement. Only law enforcement officers and members of the military are now allowed to possess assault weapons or large capacity magazines in the County.43 

50 State Summary

Key Legislative Elements

The features listed below are intended to provide a framework from which policy options may be considered.  A jurisdiction considering new legislation should consult with counsel.

  • Definition of assault weapon is based on the generic features that characterize assault weapons (California, Connecticut, New York, and the District of Columbia have the most comprehensive definitions)
  • Definition of assault weapon is based on a one-feature test (New York, the District of Columbia and Cook County each use a one-feature test for shotguns, rifles, and pistols; New Jersey uses a one-feature test for shotguns; California and Connecticut use a one-feature test for rifles and pistols)
  • Although a generic feature test is the most comprehensive approach, if the law also includes a list of banned weapons by name, it provides a mechanism authorizing an appropriate governmental official or agency to add new and/or modified models to the list (District of Columbia)
  • Definition extends to parts that may be readily assembled into an assault weapon (Connecticut and New Jersey)
  • Prohibited activities include possession, sale, purchase, transfer, loan, pledge, transportation, distribution, importation, and manufacture of assault weapons (California has the broadest prohibition)
  • Pre-ban weapons are not grandfathered and instead are to be rendered inoperable or removed from the jurisdiction (District of Columbia, Cook County; New Jersey grandfathered only a small category of assault weapons)
  • Alternatively, if pre-ban weapons are grandfathered, there is a registration mechanism for grandfathered weapons, with strict limits on their transferability, use and storage44 (California, Connecticut, Hawaii, New Jersey, New York)

  1. Different laws may define assault weapons based on the presence of different military-style features. The features identified on the diagram are drawn from the Law Center’s model assault weapons law, available from the Law Center upon request. ⤴︎
  2. For more information about these tragedies, see Mark Follman, Gavin Aronsen & Deanna Pan, A Guide to Mass Shootings in America, Mother Jones (July 20, 2012), at ⤴︎
  3. Mark Follman et al., More Than Half of Mass Shooters Used Assault Weapons and High-Capacity Magazines, Mother Jones (Feb. 27, 2013), at ⤴︎
  4. For some of the mass shootings included in the analysis, information about the types of firearms and ammunition magazines used remains unknown. Mayors Against Illegal Guns, Analysis of Recent Mass Shootings 1 (Jan. 2013), at ⤴︎
  5. Colby Goodman & Michel Marizco, U.S. Firearms Trafficking to Mexico: New Data and Insights Illuminate Key Trends and Challenges, in Shared Responsibility: U.S.-Mexico Policy Options for Confronting Organized Crime 185 (Eric L. Olson, David A. Shirk & Andrew Selee eds., 2010), at ⤴︎
  6. Violence Policy Center, “Officer Down” — Assault Weapons and the War on Law Enforcement, Section One: Assault Weapons, the Gun Industry, and Law Enforcement (May 2003), at ⤴︎
  7. International Association of Chiefs of Police (IACP), Taking a Stand: Reducing Gun Violence in Our Communities 26 (2007), at According to a survey by the Police Executive Research Forum, “Thirty-seven percent of the police agencies responding to PERF’s survey reported that they have seen noticeable increases in criminals’ use of assault weapons” since the expiration of the federal ban.” Police Executive Research Forum, Guns and Crime: Breaking New Ground by Focusing on the Local Impact 2 (May 2010), at ⤴︎
  8. See, e.g., Susan Candiotti, Cops Find Themselves in Arms Race with Criminals, Cable News Network (Nov. 6, 2007), at (last visited July 1, 2013); Kevin Johnson, Police Needing Heavier Weapons, USA Today, Feb. 19, 2007, at 1A, at ⤴︎
  9. See Taking a Stand: Reducing Gun Violence in Our Communities, supra note 7, at 26-27. ⤴︎
  10. Violence Policy Center, The Militarization of the U.S. Civilian Firearms Market 9-11, 29 (June 2011), at According to one study, Americans owned an estimated 1.5 million assault weapons as of 1994, but there is no current data about the number of these weapons privately owned today. Christopher S. Koper, An Updated Assessment of the Federal Assault Weapons Ban: Impacts on Gun Markets and Gun Violence, 1994-2003, Report to the National Institute of Justice, U.S. Department of Justice 1 (June 2004), at ⤴︎
  11. CNN/ORC International Poll, December 17-18 – Gun Rights 3 (Dec. 2012), at The public also overwhelmingly supported the renewal of the federal assault weapons ban when it expired in 2004. Seventy-seven percent of likely 2004 presidential election voters supported renewal of the federal assault weapon ban, while only 21% opposed renewal. Third Way, Taking Back the Second Amendment: Seven Steps Progressives Must Take to Close the Gun Gap 5 (Jan. 2006), at . See also Consumer Federation of America, Consumers Strongly Support Renewing and Strengthening the Federal Assault Weapons Ban 3 (Feb. 2004) (65% of Americans favored strengthening federal assault weapon ban, including 51% of gun owners). ⤴︎
  12. Field & Stream, The 2003 National Hunting Survey (July 2003), at ⤴︎
  13. 18 U.S.C. § 922(v)(1).  All references to sections of the Violent Crime Control and Law Enforcement Act of 1994, codified at 18 U.S.C. § 921 et seq., are to the sections as they appeared on September 12, 2004. ⤴︎
  14. 18 U.S.C. § 921(a)(30). ⤴︎
  15. 18 U.S.C. §§ 921(a)(31), 922(w)(1). The federal law defined “large capacity ammunition feeding device” as: “a magazine, belt, drum, feed strip, or similar device…that has a capacity of, or that can be readily restored or converted to accept, more than 10 rounds of ammunition.” 18 U.S.C. § 921(a)(31)(A). However, “attached tubular device[s] designed to accept, and capable of operating only with, .22 caliber rimfire ammunition” were exempted from the definition. 18 U.S.C. § 921(a)(31)(B). ⤴︎
  16. Koper, supra note 10, at 49. Another study analyzed data kept by the Virginia State Police and found a clear decline in the percentage of crime guns that were equipped with large capacity ammunition magazines after the federal ban was enacted.  The percentage reached a low of 10% in 2004 and then steadily climbed after Congress allowed the ban to expire; by 2010, the percentage was close to 22%.  About the Project: The Hidden Life of Guns, Wash. Post, Jan. 22, 2011, at; David S. Fallis & James V. Grimaldi, Virginia Data Show Drop in Criminal Firepower During Assault Gun Ban, Wash. Post, Jan. 23, 2011, at ⤴︎
  17. Arindrajit Dube, Oeindrila Dube, & Omar Garcia Ponce, Cross-Border Spillover: U.S. Gun Laws and Violence in Mexico (August 13, 2012). APSA 2012 Annual Meeting Paper, at SSRN: ⤴︎
  18. 18 U.S.C. §§ 922(l), 925(d)(3). Federal law also prohibits any person from knowingly receiving a firearm that was imported without authorization. 18 U.S.C. § 922(l). ⤴︎
  19. 18 U.S.C. 925(d)(3). ⤴︎
  20. 18 U.S.C. § 922(r). The law also prohibits the importation of “any frame, receiver, or barrel of such firearm which would be prohibited if assembled.” 18 U.S.C § 925(d)(3). ⤴︎
  21. Bureau of Alcohol, Tobacco and Firearms, U.S. Department of the Treasury, Department of the Treasury Study on the Sporting Suitability of Modified Semiautomatic Assault Rifles 3 (Apr. 1998), at  Previously, in 1989, ATF used this authority to limit the importation of certain semiautomatic assault rifles. Id. at 2. ⤴︎
  22. Senators Dianne Feinstein, Charles Schumer & Sheldon Whitehouse, Halting U.S. Firearms Trafficking to Mexico, Report to the U.S. Senate Caucus on Int’l Narcotics Control 13 (June 2011), at  “Many of the Romanian-manufactured AK-47s that found their way to Mexico have been imported into the United States from Europe as a whole firearm or in parts as a kit despite a U.S. ban on the importation of semi-automatic assault rifles.”  Colby Goodman & Michel Marizco, U.S. Firearms Trafficking to Mexico: New Data and Insights Illuminate Key Trends and Challenges, in Shared Responsibility: U.S.-Mexico Policy Options for Confronting Organized Crime 186 (Eric L. Olson, David A. Shirk & Andrew Selee eds., 2010), at ⤴︎
  23. Ohio also requires a special permit for the possession of a semi-automatic firearm designed or specially adapted to fire more than 31 rounds without reloading. See Ohio Rev. Code §§ 2923.11(D), (E), (K), (L), 2923.17-2923.20.  In addition to having one of the country’s strongest assault weapons bans, Connecticut also prohibits the sale or retail transfer of any semi-automatic centerfire rifle that has or accepts a magazine with a capacity exceeding five rounds to any person under twenty-one years of age.  Conn. Gen. Stat. § 29-37a(b)(2). ⤴︎
  24. Cal. Penal Code §§ 16350, 16790, 16890, 30500-31115. ⤴︎
  25. Conn. Gen. Stat. §§ 53-202a – 53-202o. ⤴︎
  26. D.C. Code Ann. §§ 7-2501.01(3A), 7-2502.02(a)(6), 7-2505.01, 7-2505.02(a), (c). ⤴︎
  27. The District of Columbia did not grandfather pre-ban assault weapons. ⤴︎
  28. Haw. Rev. Stat. Ann. §§ 134-1, 134-4, 134-8. ⤴︎
  29. Md. Code Ann., Crim. Law §§   4-301 – 4-306; Md. Code Ann., Pub. Safety § 5-101 – 5-143. ⤴︎
  30. Maryland required the registration of assault pistols, which were banned in the state many years before Maryland banned assault long guns. ⤴︎
  31. Mass. Gen. Laws ch. 140, §§ 121, 122, 123,   131, 131M. ⤴︎
  32. N.J. Stat. Ann. §§ 2C:39-1w, 2C:39-5,   2C:58-5, 2C:58-12, 2C:58-13. ⤴︎
  33. New Jersey does use a one-feature test for shotguns. ⤴︎
  34. N.Y. Penal Law §§ 265.00(22), 265.02(7), 265.10, 400.00(16-a). ⤴︎
  35. Minn. Stat. §§ 624.712 – 624.7141. ⤴︎
  36. Va. Code Ann. §§ 18.2-287.4, 18.2-308.2:01, 18.2-308.2:2, 18.2-308.7, 18.2-308.8. ⤴︎
  37. California’s definition of assault weapon also includes a semi-automatic, centerfire rifle or pistol with a fixed magazine capacity exceeding 10 rounds; a semi-automatic, centerfire rifle less than 30 inches in length; and a semi-automatic shotgun with two listed features, or the ability to accept a detachable magazine, or a revolving cylinder. ⤴︎
  38. New Jersey also bans semi-automatic rifles with a fixed magazine capacity exceeding 15 rounds. ⤴︎
  39. In 2006 California amended its law to make possession of an assault weapon a public nuisance. Cal. Penal Code § 30800. ⤴︎
  40. Registration is critical to any law that exempts pre-ban weapons. Without such a provision, it would be nearly impossible to enforce a possession ban because there would be no way to determine the date an individual acquired possession of a banned weapon. ⤴︎
  41. California and Connecticut allow possession of a grandfathered assault weapon only at, or when being transported among: the possessor’s property or workplace; the property of an expressly-consenting owner; a licensed gun dealer (for service or repair); certain target ranges; licensed shooting clubs; or an exhibition, display or education project about firearms approved by law enforcement or a recognized firearm-education entity. Cal. Penal Code § 30945; Conn. Gen. Stat. § 53-202d(f). California also allows possession of a grandfathered assault weapon on publicly owned land, provided it is specifically permitted by the managing authority. Cal. Penal Code § 30945. ⤴︎
  42. D.C. Code Ann. §§ 7-2551.01 – 7-2551.03. In 2005, Congress passed and the President signed into law the Protection of Lawful Commerce in Arms Act (PLCAA). The PLCAA grants firearms dealers and others immunity from some civil lawsuits, with certain exceptions. 15 U.S.C. §§ 7901 – 7903. ⤴︎
  43. Cook County Code of Ordinances §§ 54-211 – 54-213. ⤴︎
  44. See our summary on the Registration of Firearms for features of comprehensive registration laws. The most comprehensive system of regulating the purchase, possession and ownership of firearms combines registration of firearms with licensing of gun owners. Additional information on licensing of firearm owners is contained in our summary on Licensing Gun Owners & Purchasers. ⤴︎