This pattern reinforces the widely held notion that the right to bear arms is a vestige of a distant era. Constitutional customs tend to stick once they are enshrined, even when countries replace or revise their constitutions. While this inertia partly explains the American retention of the right to bear arms, it also shows how truly exceptional gun rights are: Countries that had the right have actively chosen to reject it in subsequent constitutions.

Constitutions with gun rights were reasonably well- represented in the late 1800s: 17 percent had the right in 1875. Since the early 1900s, however, the proportion has been less than 10 percent and falling. As new countries emerged in the interwar and post-World War II eras, their constitutions reflected a modern set of rights.

If arms were mentioned at all, it was to allow the government to regulate their use or to compel military service, not to provide a right to bear them. Today, only three out of nearly 200 constitutions contain a right to bear arms.

We have come to view constitutional rights like a one-way ratchet — their popularity moves inexorably in only one direction, and that is up. The decline in popularity of the right to bear arms indicates that there is something very different about it, as opposed to other civil, political, social and economic rights. Most probably, the right invokes an anachronism, somewhat like the protection against “quartering soldiers” in the Third Amendment to the U.S. Constitution, or it invokes moral understandings of another era.