When will politicians finally recognize that they can’t protect all the possible shooting targets?

Possibly the largest mass public shooting in US history occurred early on Sunday morning, leaving 50 dead. On Friday, also in Orlando, singer Christina Grimmie was murdered after a concert.

Both of these shootings had something in common: They both occurred in places where private citizens were banned from carrying permitted concealed handguns.

With the exception of Donald Trump, over the last few days politicians have talked about everything but gun-free zones. Hillary Clinton and President Obama have been talking background checks on the private transfers of guns or banning people who are on the “no-fly lists” from buying guns.

But not one of the mass shootings since at least 2000, including Sunday’s, would’ve been stopped by these laws. Nor would renewing the federal “assault weapons” ban solve the problem; even research paid for by Bill Clinton’s administration found no evidence the ban reduced any type of crime.

Just a couple of months ago, a young ISIS sympathizer planned a shooting at one of the largest churches in Detroit. An FBI wire recorded him explaining why he had picked the church as a target: “It’s easy, and a lot of people go there. Plus people are not allowed to carry guns in church. Plus it would make the news.”

Police are probably the single most important factor in stopping crime, but stopping a mass public shooting is an extremely dangerous proposition for officers and security guards alike. Attackers will generally first shoot any uniformed guards or officers who are present. During the Charlie Hebdo attack in Paris last year, the first person killed was the guard who was protecting the magazine’s offices.

Being able to choose the time and place of the attack gives terrorists a major strategic advantage. Last year, France learned that the hard way. In a city of 2.3 million people, there are simply too many possible targets for the police and military to protect. Parisians could take cellphone videos of terrorists just 12 yards away, but could do nothing but watch the slaughter. In the United States, we have about 628,000 police to protect 320 million Americans.

PoliceOne, a private organization with 450,000 members (380,000 full-time active law enforcement and 70,000 retired), polled its members in 2013 shortly after the Newtown, Conn., massacre. Eighty percent of respondents said allowing legally armed citizens to carry guns in places such as Newtown and Aurora would have reduced the number of casualties. Another 6 percent thought the presence of legally armed civilians would “likely” have prevented the innocent casualties altogether.

According to police and prosecutors, there have been dozens of cases of permit holders clearly stopping what would have been mass public shootings. It’s understandable these killers avoid places where they can’t kill a large number of people.

Research I have conducted with economist Bill Landes looked at 13 different types of gun-control laws. Right-to-carry laws were the only type that made a difference in the rate and severity of these mass public shootings. Such laws are like those that the 9th Circuit Court of Appeals ruled against last week, when it determined that California’s citizens didn’t have the right to protect themselves in public with concealed guns. (The open carry of guns is already illegal in California.)

President Obama has said mockingly, “Some here believe that having more guns makes us all safer.” He says we wouldn’t have these mass public shootings if that were true. However, just because there are a lot of guns in the United States doesn’t mean that people always have access to them for protection.

It ought to be common sense — even the most ardent gun-control advocate would never put “Gun-Free Zone” signs on their homes. Let’s finally stop putting them elsewhere.

John R. Lott Jr. is the president of the Crime Prevention Research Center and the author of the forthcoming “War on Guns.”