Evidence was insufficient to determine the effectiveness of any of these laws for the following reasons.
•Bans on specified firearms or ammunition.
Results of studies of firearms and ammunition bans were inconsistent: certain studies indicated decreases in violence associated with bans, and others indicated increases. Several studies found that the number of banned guns retrieved after a crime declined when bans were enacted, but these studies did not assess violent consequences (16,17). Studies of the 1976 Washington, D.C. handgun ban yielded inconsistent results (18--20). Bans often include "grandfather" provisions, allowing ownership of an item if it is acquired before the ban, complicating an assessment of causality. Finally, evidence indicated that sales of firearms to be banned might increase in the period before implementation of the bans (e.g., the Assault Weapons Ban of 1994) (21).
•Restrictions on firearm acquisition.
The federal government and individual states restrict the acquisition and use of firearms by individuals on the basis of their personal history. Reasons for restriction can include prior felony conviction, conviction of misdemeanor intimate partner violence, drug abuse, adjudication as "mentally defective,"†† and other characteristics (e.g., specified young age). The Brady Law (22) established national restrictions on acquisition of firearms and ammunition from federal firearms licensees. The interim Brady Law (1994--1998) mandated a 5-day waiting period to allow background checks. The permanent Brady Law, enacted in 1998, eliminated the required waiting period. It normally allows 3 days for a background check, after which, if no evidence of a prohibited characteristic is found, the purchase may proceed (23). Certain states have established additional restrictions, and some require background checks of all firearms transactions, not only those conducted by federal firearms licensees.
The permanent Brady Law depends on the National Instant Criminal Background Check System (NICS). However, NICS lacks much of the required background information, particularly on certain restriction categories (23). Efforts to improve the availability of background information have been supported by the National Criminal History Improvement Program (24). Approximately 689,000 applications to acquire a firearm (2.3% of 30 million applications) were denied under the Brady Law from its first implementation in 1994 through 2000 (25); the majority of denials were based on the applicant's criminal history. However, denial of an application does not always stop applicants from acquiring firearms through other means.
Overall, evaluations of the effects of acquisition restrictions on violent outcomes have produced inconsistent findings: some studies indicated decreases in violence associated with restrictions, and others indicated increases. One study indicated a statistically significant reduction in the rate of suicide by firearms among persons aged >55 years; however, the reduction in suicide by all methods was not statistically significant. Furthermore, this benefit appears to have been a consequence of the waiting period imposed by the interim Brady Law (which has since been dropped in the permanent law) rather than of the law's restrictions on the basis of the purchaser's characteristics (26).
•Waiting periods for firearm acquisition.
Waiting periods for firearm acquisition require a specified delay between application for and acquisition of a firearm. Waiting periods have been established by the federal government and by states to allow time to check the applicant's background or to provide a "cooling-off" period for persons at risk of committing suicide or impulsive acts against others. Studies of the effects of waiting periods on violent outcomes yielded inconsistent results: some indicated a decrease in violent outcome associated with the delay and others indicated an increase. As noted previously, one study of the interim Brady Law indicated a statistically significant reduction in firearms suicide among persons aged >55 years associated with the waiting period requirement of the interim law. Several studies suggested a partial "substitution effect" for suicide (i.e., decreases in firearms suicide are accompanied by smaller increases in suicide by other means) (26).
•Firearm registration and licensing of owners. Registration requires that a record of the owner of specified firearms be created and retained (27). At the national level, the Firearm Ownership Protection Act of 1986 specifically precludes the federal government from establishing and maintaining a registry of firearms and their owners. Licensing requires an individual to obtain a license or other form of authorization or certification to purchase or possess a firearm (27). Licensing and registration requirements are often combined with other firearms regulations, such as safety training or safe storage requirements. Only four studies examined the effects of registration and licensing on violent outcomes; the findings were inconsistent.
•"Shall issue" concealed weapon carry laws.
Shall issue concealed weapon carry laws (shall issue laws) require the issuing of a concealed weapon carry permit to all applicants not disqualified by specified criteria. Shall issue laws are usually implemented in place of "may issue" laws, in which the issuing of a concealed weapon carry permit is discretionary (based on criteria such as the perceived need or moral character of the applicant). A third alternative, total prohibition of the carrying of concealed weapons, was in effect in six states in 2001.
The substantial number of studies of shall issue laws largely derives from and responds to one landmark study (28). Many of these studies were considered to be nonindependent because they assessed the same intervention in the same population during similar time periods. A review of the data revealed critical problems, including misclassification of laws, unreliable county-level crime data, and failure to use appropriate denominators for the available numerator crime data (29). Methodological problems, such as failure to adjust for autocorrelation in time series data, were also evident. Results across studies were inconsistent or conceptually implausible. Therefore, evidence was insufficient to determine the effect of shall issue laws on violent outcomes.
•Child access prevention laws.
Child access prevention (CAP) laws are designed to limit children's access to and use of firearms in homes. The laws require firearms owners to store their firearms locked, unloaded, or both, and make the firearm owners liable when children use a household firearm to threaten or harm themselves or others. In three states with CAP laws (Florida, Connecticut, California), this crime is a felony; in several others it is a misdemeanor.
Only three studies examined the effects of CAP laws on violent outcomes, and only one outcome, unintentional firearms deaths, was assessed by all three. Of these, two studies assessed the same states over the same time periods and were therefore nonindependent. The most recent study, which included the most recent states to pass CAP laws and had the longest follow-up time, indicated that the apparent reduction in unintentional firearm deaths associated with CAP laws that carry felony sanctions was statistically significant only in Florida and not in California or Connecticut (30). Overall, too few studies of CAP law effects have been done, and the findings of existing studies were inconsistent. In addition, although CAP laws address juveniles as perpetrators of firearms violence, available studies assessed only juvenile victims of firearms violence.
•Zero tolerance laws for firearms in schools.
The Gun-Free Schools Act (31) stipulates that each state receiving federal funds must have a state law requiring local educational agencies to expel a student from school for at least 1 year if a firearm is found in the student's possession at school. Expulsion may lead to alternative school placement or to "street" placement (full expulsion, with no linkage to formal education). In contrast to the 3,523 firearms reported confiscated under the Gun-Free Schools Act in the 1998--99 school year, school surveys (32) indicate that an estimated 3% of the 12th grade student population in 1996 (i.e., 85,350 students) reported carrying firearms on school property one or more times in the previous 30 days. Thus, even if only 12th grade students carry firearms, fewer than 4.3% of firearms are being detected in association with the Gun-Free Schools Act.
No study reviewed attempted to evaluate the effects of zero tolerance laws on violence in schools, nor did any measure the effect of the Gun-Free Schools Act on carrying of firearms in schools. One cross-sectional study, however, assessed the effectiveness of metal detector programs in reducing the carrying of firearms in schools (33). Although firearms detection is not explicitly required in the Gun-Free Schools Act, the effectiveness of the law may depend on the ability to detect firearms by various means. The study reported that schools with and without metal detectors did not differ in rates of threatening, fights, or carrying of firearms outside of school, but the rate of carrying firearms to, from, or in schools with detection programs was half that of schools without such programs. The effectiveness of zero tolerance laws in preventing violence cannot be assessed because appropriate evidence was not available. A further concern is that "street" expulsion might result in increased violence and other problems among expelled students.
•Combinations of firearms laws.
Governmental jurisdictions (e.g., states or nations) can be characterized by the degree to which they regulate firearm possession and use. Whether a greater degree of firearms regulation in a jurisdiction results in a reduction of the amount of violence in that jurisdiction still needs to be determined. Three kinds of evidence were reviewed for this study: 1) studies of the effects of comprehensive national laws within nations; 2) international comparisons of comprehensive laws; and 3) studies in which law types within jurisdictions (i.e., regulation of specific, defined aspects of firearm acquisition and use) were categorized and counted, and counts compared with rates of specific forms of violence within the same jurisdictions. The latter type are referred to here as index studies because they developed indices of the degree of regulation. In drawing conclusions about law combinations, findings from the three approaches were considered.
On the basis of national law assessments (the Gun Control Act of 1968 in the United States and the Criminal Law Amendment Act of 1977 in Canada), international comparisons (between the United States and Canada), and index studies (all conducted within the United States), available evidence was insufficient to determine whether the degree of firearms regulation was associated with decreased (or increased) violence. The findings were inconsistent and most studies were methodologically inadequate to allow conclusions about causal effects. Moreover, as conducted, index studies, even if consistent, would not allow specification of which laws to implement.
In summary, the Task Force found insufficient evidence to determine the effectiveness of any of the firearms laws reviewed for preventing violence. References and key findings are listed (Table).
