ROMULUS, MI - APRIL 27: A supporter of Michigan's Open Carry law attends a rally and march April 27, 2014 in Romulus, Michigan. The march was held to attempt to demonstrate to the general public what the typical open carrier is like. (Photo by Bill Pugliano/Getty Images)

Gun-rights activists have shot themselves in the foot, again, with a gun rally that caused another major American retail chain to declare firearms unwelcome.

Chipotle on Monday said it wanted customers to stop bringing guns to its restaurants, after photos of an open-carry rally at one of its Dallas restaurants went viral -- thanks in part to the shrewd social-media campaign of a gun-control group. The striking photos showed a dozen or so people brandishing firearms, including semiautomatic rifles, both inside and outside the restaurant.

"The display of firearms in our restaurants has now created an environment that is potentially intimidating or uncomfortable for many of our customers," a spokesman for Chipotle, which has about 1,600 U.S. stores, said in a statement.

After the open-carry rally on Saturday, the gun-control group Moms Demand Action for Gun Sense in America launched a campaign on Twitter and Facebook with the hashtag #burritosnotbullets. Front and center in the group's posts were photos from the event.

In asking customers not to bring guns into its stores -- a decision that falls short of an outright ban, which would likely be impossible to enforce -- Chipotle became the latest major American company to wade into the national gun debate.

Starbucks CEO Howard Schultz last September declared that guns were unwelcome at the ubiquitous coffee chain, under similar circumstances. Open-carry advocates had staged a series of "Starbucks Appreciation Days," wielding guns in Starbucks outlets around the country. Moms Demand Action, which was founded in the aftermath of the Newtown, Connecticut, massacre, successfully pressed Starbucks to ask owners to leave their guns at home.

The mom's group also got Facebook and Instagram to issue new rules in March meant to stem gun sales on the social-media sites.

The gun-control group had less success in persuading the office-supply store Staples to ban guns. And it is currently fighting a rearguard action in many Southern states that have loosened restrictions on where citizens can carry concealed weapons. Most recently, Georgia enacted a so-called "guns everywhere" law, which, among other things, makes it legal for parishioners to bring guns to Sunday school.

Despite these setbacks, Moms Demand action, which recently teamed up with former New York Mayor Michael Bloomberg's Mayors Against Illegal Guns, has clearly struck a nerve -- both with gun opponents and with people who might support gun rights, but don't think they should be extended to allowing armed people to brandish large weapons wherever they choose. And by forcing businesses into the debate, they have managed to claim success when victories for the movement have been rare.

In fact, the aftermath of the Newtown shootings has largely been a disaster for gun-control activists. Legislation that would ban certain type of assault rifles and ammunition and eliminate widely-exploited background-check loopholes was bludgeoned to death by the National Rifle Association. As of December, according to the New York Times, states had passed 70 laws loosening gun restrictions since Newtown, compared with 39 laws tightening them.

And that was before Georgia and South Carolina loosened their fetters. (Gun control activists have had some scattered success at the legislative level, most recently convincing a handful of states, including Wisconsin, to pass laws restricting the ability of people convicted of domestic violence crimes from obtaining firearms).

Despite an uptick in fundraising and a pledge by Bloomberg to spend $50 million to oppose anti-gun-control candidates, the NRA and its allies remain vastly better funded -- and better connected to state and federal politicians.

Businesses, by contrast, are in some ways more democratic institutions than legislatures. Every day, they must seek to appeal to the broadest possible base of customers. It is hard to imagine that most parents, even in conservative states, are comfortable dining next to a group of people toting large weapons. By distributing photos that show just what that looks like, Moms Demand Action has hit on an effective strategy.