The headline on last Sunday's Chicago Tribune was stark and arresting: "A thousand shootings." That's what Chicago experienced in the first six months of 2013. It works out to more than five a day.

So what crime issue got Gov. Pat Quinn worked up last week? The danger posed by Illinoisans holding state permits to carry concealed firearms. "My foremost duty as governor is to keep the people of Illinois safe," he said in issuing an amendatory veto of a bill to legalize concealed-carry in the last state without it.

His changes included a ban on carrying guns in establishments that serve alcohol and limiting each carrier to one gun with a magazine holding a maximum of 10 rounds. But in the end they didn't matter, because the General Assembly overrode his veto. The new law sets up a system obliging the state to issue licenses to registered gun owners who pass a background check, undergo 16 hours of safety training and pay a fee.

Quinn responded: "Following a weekend of horrific violence in Chicago in which at least 70 people were shot and 12 killed, this was the wrong move for public safety in Illinois." But of those 70 shootings—or the 1,000-plus shootings that preceded them this year — it's safe to wager that few if any involved legal weapons used by individuals legally entitled to own them.

It's exceptionally rare for a previously law-abiding person to take a legally purchased firearm, load it, walk out the door and shoot someone. But that's the specter that dominates the mind of Quinn when the subject of concealed-carry comes up. It also preoccupies Chicago Mayor Rahm Emanuel.

The problem of gun violence in the city, though, is a problem of violence committed by criminals and juveniles who are not allowed to own guns, much less carry them in public. To worry about legal permit holders in that context is like fretting that you may have left a faucet running as you try to escape a flood.

The discussion arises because of a federal appeals court decision last year striking down Illinois' ban on concealed-carry. Noting that the Supreme Court says the Second Amendment guarantees the right to have guns in the home for protection, it concluded there is no logic in denying individuals that means of self-defense in public spaces.

"A right to bear arms," wrote Judge Richard Posner, "thus implies a right to carry a loaded gun outside the home." The court gave the state six months to create a permit system.

Chicago Democrats act as though this is either a) a surefire formula for more bloodshed or b) a reckless leap into the unknown. It's neither. In recent years, we have accumulated a wealth of evidence about what happens when a state establishes a "shall-issue" system under which qualified citizens may pack pistols.

Since Florida blazed the trail in 1987, state after state has followed. During that period, the national homicide rate has fallen by more than 40 percent. Florida's dropped even faster. Back then, its murder rate was far higher than Illinois'. By 2011, it was lower.

It would be too much to assume that the spread of concealed-carry accounts for the improvement. Lots of factors have produced the national reduction in violent crime. But it hasn't gotten in the way.

Opponents, however, never tire of insisting that letting individuals tote firearms will unleash mass carnage. The Washington-based Violence Policy Center makes much of the fact that since 2007, by its count, 516 people have been killed by permit holders.

But a quarter of those were suicides, which are not a danger to public safety. Though the figure sounds high, it's less than 90 a year—in a country with more than 50,000 homicides and suicides annually.

The number of licensees who make lethal misuse of their guns, likewise, is a microscopic percentage of the estimated 6 million people who are authorized to carry. The overwhelming majority behave in a responsible, lawful way. The people behind the epidemic of violent crime in Chicago, by contrast, don't bother with permits and wouldn't qualify for them.

For this group, the new law is irrelevant. Politicians who use the ongoing slaughter as a reason to oppose it only confirm that when it comes to government's most important function, they haven't got a clue.