Every time a horrific crime committed with a gun gets national attention, politicians will usually recommend more stringent gun laws as a response. (With the phrase "gun control" out of vogue, you usually hear these days about "common sense gun safety laws.")

The New York Times, who last year ran a nearly unprecedented front-page editorial calling for the banning and confiscation of a commonly used and rarely abused class of civilian firearms, investigated today how and whether laws, either existing or proposed, would have impacted "all 130 shootings last year in which four or more people were shot, at least one fatally, and investigators identified at least one attacker."

The overarching conclusion from reporters Sharon LaFraniere and Emily Palmer? They learned "not only how porous existing firearms regulations are, but also how difficult tightening them in a meaningful way may be."

"The findings are dispiriting to anyone hoping for simple legislative fixes to gun violence," they admit upfront:

In more than half the 130 cases, at least one assailant was already barred by federal law from having a weapon, usually because of a felony conviction, but nonetheless acquired a gun. Including those who lacked the required state or local permits, 64 percent of the shootings involved at least one attacker who violated an existing gun law. Of the remaining assailants, 40 percent had never had a serious run-in with the law and probably could have bought a gun even in states with the strictest firearm controls. Typically those were men who killed their families and then themselves.

Slightly over 10 percent of these mass shootings involved an "assault rifle," the rest involved handguns. (Of overall homicides in America, rifles as an entire category are involved in about 2 percent as of 2014 data, fewer than murders committed via bare hands or feet.)

The Times looks at those "more than half" where a perfectly enforced law should have prevented a killer from getting a gun. This gets at the question of whether expanding background check requirements beyond licensed dealers, per current federal law, would indeed save lives by making it illegal for anyone to sell a gun to anyone without conducting a background check into legally disqualifying factors.

Unfortunately as far as the information gathered by the Times's reporters go:

It was virtually impossible to determine whether expanded background checks would have deterred the illegally armed attackers involved in the shootings examined for this article. In many cases, police officers never recovered the weapons, and even when they did, they did not always investigate where the firearm came from. A trace by the federal Bureau of Alcohol, Tobacco, Firearms and Explosives generally shows only the original seller and buyer, while the typical gun used in a crime is 11 years old.

The Times tells a story of one man with 12 years in prison who killed 8 people, including 6 children, with a gun they think he bought online. (The reporters admit they aren't absolutely sure of that.) That would have already been illegal.

It isn't always true that laws that are easy to break are pointless laws. But laws that are far more likely to merely end up fining or imprisoning people performing an action that would not actually harm anyone (that is, selling a gun that would never be used to harm anyone else to someone without informing the state or running a background check) than they would be to prevent harm to others should be reasonably questioned.

The story wonders whether public safety demands that our standards for barring people from gun ownership for mental health issues be more stringent, noting that current federal law "denies guns only to people who have been involuntarily committed for inpatient treatment" and lamenting that since that law was passed in 1968, it's often more complicated and less likely that that happens to an American.

After noting some states with existing or prospective laws that make it harder to legally get a gun for people who have interacted with the mental health system or alarmed their family members with their behavior, they find that:

No such provisions were in place in the states where mentally ill gunmen carried out nine of the 130 shootings last year. Police inquiries into several cases later showed that family and household members feared disaster in the making, but felt helpless to avert it.

They tell a detailed story of a particular eventual killer who said all sorts of alarming and threatening things about thinking of killing people to all sorts of people, none of which ended up preventing him from using guns he'd bought online, according to the Times, to kill three people (including an 11-year-old girl) and then himself.

They tell another story of a Georgia man who had spent some time in an mental institution, though not technically involuntarily committed, a situation that in five states and D.C. "would have meant at least a temporary ban on firearm purchases. But like most states, Georgia follows the looser federal standard."

He bought many guns, had his concerned father lock the ones he knew about away. But using a pistol his father did not know about, he killed two people in a liquor store before himself being shot at by another armed customer and fleeing. (Police told the Times that this was only one of 2 cases of these 130 in which an innocent armed citizen "fired back in a clear-cut case of self-defense.")

The Times tells another detailed story of a man who had made threatening comments, including one that got him a visit from the cops. He was nonetheless legally able to buy a gun, passing a background check because he'd committed no disqualifying on-the-books crime. He then went on to murder a family of neighbors; the Times notes the murdered father owned a handgun for self-defense but did not have the opportunity to use it.

The very long Times story goes on and on with more anecdotes of people who killed people while doing things (even before the illegal act of murder) that perhaps could have been against the law, like open carrying a rifle in the street, or having a legally owned weapon locked in your vehicle on a college campus.

The first anecdote implies that had open-carry not been legal, police would have come and apprehended him before he killed three people with the weapon he was carrying; the second that an angry guy in a fraternity prank dispute might not have had his gun available near him to go nuts and start shooting in what was just a dumb college kid conflict.

The detailed anecdotes in the story are all infuriating and will doubtless make most readers think, if a properly enforced law could have prevented this, it would be worth it.

The story does not think out loud about the costs and tragic stories that might result if, say, police felt it a duty to confront everyone who is carrying a weapon in public where it's legal. It doesn't bring up the personal and social costs of creating another officious excuse for police to search and punish people for the crime of buying or possessing something that they would never use to harm another, like the vast, vast majority of gun owners, including those in prohibited categories.

The story trails off into a series of those detailed, sad stories long after it mentions, then doesn't mention again, the overall conclusion at the start from studying those 130 incidents of mass murder and injury: that even the toughest laws in a world where guns exist could not even conceivably have prevented 40 percent of them, and that when laws in theory perhaps should have prevented a potential killer from owning a gun, they were easily breakable.

And remember: such perfectly enforced laws would be far more likely to bedevil and harass the innocent for selling and owning items they would never use to harm anyone illegitimately than they would be to prevent one of the Times detailed tragic (but thankfully quite rare compared to the number of gun owners in America) anecdotes from happening.

More about what we know, and don't know, about the efficacy of gun laws in my Reason feature "You Know Less Than You Think About Guns." As this Times story also makes clear at the start then tries to muddy up via tragic storytelling, we don't have much of a reason to believe that most proposed new gun laws would do much good, and as the Times story does not acknowledge, by creating many more excuses for the law to harass the innocent, we know they could do harm.