It’s a phenomenon that gives the term “gun control” a whole new meaning: community ordinances that encourage citizens to own guns.

Last month, Greenleaf, Idaho, adopted Ordinance 208, calling for its citizens to own guns and keep them ready in their homes in case of emergency. It’s not a response to high crime rates. As The Associated Press reported, “Greenleaf doesn’t really have crime… the most violent offense reported in the past two years was a fist fight.” Rather, it’s a statement about preparedness in the event of an emergency, and an effort to promote a culture of self-reliance.

And it may not be a bad idea. While pro-gun laws like the one in Greenleaf are mostly symbolic, to the extent that they actually make a difference, it is likely to be a positive one.

Greenleaf is following in the footsteps of Kennesaw, Ga., which in 1982 passed a mandatory gun ownership law in response to a handgun ban passed in Morton Grove, Ill. Kennesaw’s crime dropped sharply, while Morton Grove’s did not.

To some degree, this is rational. Criminals, unsurprisingly, would rather break into a house where they aren’t at risk of being shot. As David Kopel noted in a 2001 article in The Arizona Law Review, burglars report that they try to avoid homes where armed residents are likely to be present. We see this phenomenon internationally, too, with the United States having a lower proportion of “hot” burglaries — break-ins where the burglars know the home to be occupied — than countries with restrictive gun laws.

Likewise, in the event of disasters that leave law enforcement overwhelmed, armed citizens can play an important role in stanching crime. Armed neighborhood watches deterred looting in parts of Houston and New Orleans in the aftermath of Hurricanes Katrina and Rita.

Precisely because an armed populace can serve as an effective backup for law enforcement, the ownership of firearms was widely mandated during Colonial times, and the second Congress passed a statute in 1792 requiring adult male citizens to own guns.

The twin purposes of self and community defense may very well lie behind the Second Amendment’s language encompassing both the importance of a well-regulated militia and the right of citizens to keep and bear arms. As the constitutional and criminal law scholar Don Kates has noted in the journal Constitutional Commentary, thinkers at the time when the Constitution was written drew no real distinction between resisting burglars, foreign invaders or domestic tyrants: All were wrongdoers that good citizens had the right, and the duty, to oppose with force.

Greenleaf’s ordinance is consistent with this approach. But it may also serve another purpose.

Experts don’t think the Kennesaw ordinance, which has never actually been enforced, did much to change gun ownership rates among Kennesaw residents. And, given that Greenleaf’s mayor has estimated that 80 percent of the town’s residents already own guns, the new ordinance can’t make all that much of a difference. But criminals are likely to suspect that towns with laws like these on the books will be unsympathetic to malefactors in general, and to conclude that they will do better elsewhere.

To the extent that’s true, we’re likely to see other communities adopting similar laws so that criminals won’t see them as attractive alternatives. The result may be a different kind of “gun control.”

Glenn Reynolds, a law professor at the University of Tennessee, is the author of the blog Instapundit and of An Army of Davids: How Markets and Technology are Empowering Ordinary People to Take on Big Government, Big Media and Other Goliaths.