Of course, gun manufacturers are legitimate businesses, as are the financial services companies that fund them. On Monday, in a dissenting opinion, Justice Clarence Thomas spoke to this in bemoaning the Supreme Court’s refusal to hear a Second Amendment challenge to a Chicago suburb’s ordinance that banned certain weapons.

“The overwhelming majority of citizens who own and use such rifles do so for lawful purposes, including self-defense and target shooting,” Justice Thomas wrote. “Under our precedents, that is all that is needed for citizens to have a right under the Second Amendment to keep such weapons.”

In attacking the gun industry, Ms. James is taking a page from other successful efforts to pressure “sin” industries like cigarettes and coal. While seeking divestments has long been popular, they have had little direct impact, according to studies, despite the headlines they often generate.

But efforts to prevent banks and other financing sources from lending money to certain companies has been far more effective. For instance, as chronicled in this column earlier this year, a number of advocacy groups successfully ended the practice of mountaintop removal of coal in Appalachia, an environmentally devastating practice, by pressuring banks like Bank of America, Citigroup, Morgan Stanley, JPMorgan Chase, Wells Fargo and Credit Suisse to choke off funding, which they did over nearly a decade of pressure.

Leah Gunn Barrett, executive director of New Yorkers Against Gun Violence, who is involved in the Campaign to Unload, said this tactic could have an impact. “They are impervious to public polls,” she said. “It is all about money for them.”

Last week, Stop Handgun Violence, a gun control organization based in Newton, Mass., also looked to use financial levers as it continued to wage its campaign against Remington Outdoor (formerly the Freedom Group), the gun manufacturer owned by Cerberus Capital Management, a private equity firm. One of the guns used in San Bernardino was a Bushmaster AR-15, a Remington Outdoor brand.

After Sandy Hook, which also involved a Bushmaster rifle, several public pension funds that had money invested in Cerberus called on it to sell the company. Cerberus publicly pledged to sell, but after an unsuccessful auction, decided to maintain ownership while allowing investors to sell their stakes. Last spring, it bought out investors like the California State Teachers’ Retirement System, but maintained ownership of the company. Privately, the firm told investors it would be unfair to sell the company at a huge loss for investors who didn’t have a problem with owning a gun maker.