In some countries such as the United States, the amount of regulation that governments should impose on firearms is controversial. One major point in the argument is the positive or negative correlation that many argue exist between crime, especially violent crime, and gun ownership. Both sides actively debate the relevance of gun laws and self-defense in modern society.

Some scholars, notably John Lott, claim to have discovered a positive correlation between gun control legislation and crimes in which criminals confront citizens. Robert Ehrlich, in his book Nine Crazy Ideas in Science (ISBN 0691094950), examines this issue in Chapter 2, "More Guns Means Less Crime". He revisits John Lott's original data and concludes that the data was somewhat manipulated to "prove" a point. For example, many graphs are fits to the data and do not show the data itself. The raw data does not support Lott's thesis the way the fitted graph did. Ehrlich's conclusion is that more guns does not mean less crime, though it does not necessarily mean more crime either.

A European example would be to compare the violent crime levels between the United Kingdom which has very strict rules against gun ownership and self-defense and Switzerland which has widespread private gun ownership and which maintains the right to self-defense. According to Interpol data, in 2002, homicides were significantly more prevalent (2.91 vs 2.01 per 100,000 inhabitants) in Switzerland than in England and Wales [1] [2]. This would seem to indicate a positive correlation between gun ownership and crime. Such a comparison between only two countries, however, is quite meaningless: many other factors may come into play except for firearm legislation. As an element of comparison, in 2001 the homicide rate for the United States of America was 5.91 per 100,000 [3].

Another example is Japan,which has strict rules about gun ownership and a low crime rate.

The 1993 US Brady Bill is an example of a gun control law that has been generally correlated with a decrease, not an increase, in overall crime levels. Critics argue that the reduction was more driven by improving economic and other factors than by the gun control regulations. Because the Brady Bill was a national law, the measurement of its results must be treated as a single sample. That is, it has no more nor less weight than the findings after a change in the laws of a single state or municipality.

See gun politics.