After the failure of Senate legislation to expand background checks for gun purchases, President Obama told the press,

"I've heard some say that blocking this step would be a victory," Obama said. "My question is: A victory for who? A victory for what? All that happened today was the preservation of the loophole that lets dangerous criminals buy guns without a background check."

Obama called the defeat a "shameful day" for America. In those sentiments, he was joined by shooting victim and former Rep. Gabby Giffords (D-Ariz.), who said,

"The U.S. Senate decided to do the unthinkable about gun violence — nothing at all," Giffords wrote in an e-mail to supporters. "It's clear to me that if members of the U.S. Senate refuse to change the laws to reduce gun violence, then we need to change the members of the U.S. Senate."

Such reactions are understandable but misplaced. Whatever else you can say about the bipartisan bill authored by Sen. Joe Machin (D-W.V.) and Sen. Pat Toomey (R-Pa.), the plain fact is that it would have little to no impact on future mass shootings or other gun-related crime. The legislation would have made more gun transfers subject to the federal database that lists prohibited purchasers and would have expanded the categories of people subject to rejection. A call by Sen. Dianne Feinstein (D-Calif.) to reinstate a ban on so-called assault weapons also failed, causing the Golden State lawmaker to say, "The despair and the dismay of families standing out there whose safety we need to protect, and we don't do it." Feinstein had implored her Senate colleagues to "show some guts" by voting for her legislation.

But there are at least three reasons why the Manchin-Toomey bill—along with other recenty failed attempts to limit magazine capacities and ban assault weapons—would do little or nothing to reduce gun violence or prevent the next mass shooting. The reasons include:

1. Criminals—including mass shooters—don't buy their guns legally. As Jacob Sullum recently pointed out, surveys of inmates found that they overwhelmingly get their guns either illegally or by other means that won't be affected by any new laws:

Three sources accounted for almost nine out of 10 crime guns: "friends or family" (40 percent), "the street" (38 percent), and theft (10 percent). It is hard to see how any notional background check requirement, even one applying to all private transfers, can reasonably be expected to have a significant impact on these sources. As usual with gun control, the attempt to enforce such a requirement would impose costs and uncertain legal risks on law-abiding gun owners while leaving criminals free to go about their business.

For all the anxiety caused by so-called gun-show loophole, through which private sales at gun shows are not necessarily subject to background checks, just 2 percent of inmates said they got their guns that way.

2. The last assault weapons ban had no clear effect on gun-related violence. A 2004 study for the National Institute of Justice at the Dept. of Justice concluded that the assault weapons ban, which also regulated "large-capacity magazines" (LCMs), that lasted from 1994-2003 did not have an easily observed impact on gun crime. Gun-violence rates did decline over that period, but the researchers wrote, "we cannot clearly credit the ban with any of the nation's recent drop in gun violence." That's because such weapons were rarely used in gun crimes even before the ban. As important, the authors wrote that were an assault weapons ban reinstated, "the ban's effects on gun violence are likely to be small at best and perhaps too small for reliable measurement."

3. Gun-related violence and overall violent crime is declining. Tragedies such as the Newtown shooting last December provoke a strong emotional reaction. That's understandable and we need to pay attention to the fears, anxieties, and pain such horrific events cause. But it's also imperative that we don't legislate out of panic of raw emotions—that sort of thing leads to, say, the internment of Japanese-American citizens during World War II and the passage of The Patriot Act.

Indeed, the first point of discussion regarding gun control should be the large trends of the past 20 years—a period in which most states have greatly liberalized their gun laws and the Supreme Court has made decisions strengthening Second Amendment rights for individuals to own and bear arms. Far from unleashing a torrent of gun-related violence, the opposite has occurred:

In 1992…the violent crime rate per 100,000 residents was 758. In 2012, it was 386. Between 2000 and 2009 (the latest year for which I could easily find data) use of firearms in violent crime had decreased from a rate of 2.4 per 1,000 to 1.4 per 1,000.

And surely it matters that there is no evidence that mass shootings are on the rise in recent years. They are always terrifying and appalling but they are also rare.

Contemporary politics is in many ways mostly symbolic: Laws are passed less to effect real change than to "signal" that we care or to "show" what sort of country we are. As with the powerfully emotional responses to the mass killing of schoolkids—or the horror of terrorist bombs exploding at the Boston Marathon—this is totally understandable. But it's simply no basis for effective laws that will actually make us safer or better off.