As Stanford law professor John Kaplan has observed, "When guns are outlawed, all those who have guns will be outlaws."Kaplan argued that when a law criminalizes behavior that its practitioners do not believe improper, the new outlaws lose respect for society and the law. Kaplan found the problem especially severe in situations where the numbers of outlaws are very high, as in the case of alcohol, marijuana, or gun prohibition.
Even simple registration laws meet with massive resistance. In Illinois, for example, a 1977 study showed that compliance with handgun registration was only about 25 percent. A 1979 survey of Illinois gun owners indicated that 73 percent would not comply with a gun prohibition. It is evident that New York City's almost complete prohibition is not voluntarily obeyed; estimates of the number of illegal handguns in the city range from one million to two million. With more widespread American gun control, the number of new outlaws would certainly be huge. Prohibition would label as criminal the millions of otherwise law-abiding citizens who believe they must possess the means to defend themselves, regardless of what legislation dictates.
In addition, strict enforcement of gun prohibition--like our current marijuana prohibition and our past alcohol prohibition--would divert enormous police and judicial resources to ferreting out and prosecuting the commission of private, consensual possessory offenses. The diversion of resources to the prosecution of such offenses would mean fewer resources available to fight other crime.
Assume half of all current handgun owners would disobey a prohibition and that 10 percent of them would be caught. Since the cost of arresting someone for a serious offense is well over $2,000, the total cost in arrests alone would amount to $5 billion a year. Assuming that the defendants plea-bargained at the normal rate (an unlikely assumption, since juries would be more sympathetic to such defendants than to most other criminals), the cost of prosecution and trial would be at least $4.5 billion a year. Putting each of the convicted defendants in jail for a three-day term would cost over $660 million in one-time prison construction costs, and over $200 million in annual maintenance, and would require a 10 percent increase in national prison capacity. Given that the entire American criminal justice system has a total annual budget of only $45 billion, it is clear that effective enforcement of a handgun prohibition would simply be impossible.