If Oklahoma prison authorities had been able to carry out Clayton Lockett’s execution using sodium thiopental, his death on April 29 would likely have been swift and relatively painless. The powerful sedative used to be part of the standard lethal-injection drug combination, but when its only American manufacturer stopped production in 2010, European governments barred pharmaceutical companies on the other side of the Atlantic from exporting sodium thiopental to the United States.

As the British business secretary, Vince Cable, made clear at the time, the point of the ban was to strike a moral pose. “This move underlines this government’s and my own personal moral opposition to the death penalty in all circumstances,” he said. The practical effect, however, has been to drive death-penalty states to devise new lethal injection protocols, sometimes with gruesome results.

Many Americans would say that Lockett’s prolonged death was no less than he deserved for the vicious murder of 18-year-old Stephanie Neiman in 1999. But justice for murder victims isn’t what the Europeans have in mind. They just want to demonstrate their antipathy to capital punishment. Refusing to sell the drugs that can make lethal injections the most humane form of execution enhances their self-image. It also turned Lockett’s death from a rapid act of euthanasia into a grimacing, teeth-clenching ordeal that finally ended with a heart attack after more than 40 minutes.

There is a lesson here about the unintended consequences of economic boycotts that backers of the fossil-fuel divestment movement would do well to contemplate.

On college campuses across the country, activists have been urging administrators to adopt “fossil-free” investment policies and rid their endowment funds of shares in coal, oil, and gas stocks. Last week, Stanford became the first major university to join the boycott, announcing its intention to stop investing in “companies whose principal business is the mining of coal.” Though Stanford’s endowment, about $19 billion, is substantial, its actual investments in coal stocks are minimal. Divesting them will have no real financial impact on either the university or the companies. But it strikes a moral pose, and adds to the pressure on other universities to do likewise.

The biggest target of the divestment movement is Harvard, with its $32 billion endowment and outsize reputation. A student group, Divest Harvard, recently blocked the entrance to Massachusetts Hall, the university’s main administration building, as part of a campaign to pressure the school to get rid of its fossil-fuel holdings. So far the university has said no, on the grounds that the endowment’s purpose is to earn the income on which many Harvard priorities rely, and that “barring investments in a major, integral sector of the global economy would … come at a substantial economic cost.”

Blockading the administration building may feel like disobedience in a righteous cause; students clamoring for hydrocarbon divestment may be convinced they’re on the side of the angels. Are they convinced enough to risk the consequences of a weaker endowment? Such as less of the financial aid with which Harvard subsidizes 70 percent of its students?

You don’t have to be an especially savvy investor to realize that divestment for ideological reasons doesn’t increase your leverage, it eliminates it. Sell your profitable fossil-fuel stocks to show your concern about climate change, and the odds are they’ll be snapped up by investors who care much less about the issue than you do. “It’s like believing that pornography is evil,” writes Canadian economist Todd Hirsch, “so you sell your stash of nudie magazines to the teenager next door.”

Using economic weapons for ideological reasons so often leads to unintended and unwanted consequences. Prohibition triggered a host of negative outcomes that its promoters never anticipated, from a wave of restaurant failures to the elimination of thousands of blue-collar jobs to an explosion of crime and corruption.

To stigmatize fossil fuels and the corporations that extract them is to stigmatize the energy on which the modern world runs. This is moral preening, the hypocrisy of activists who want to strike a noble pose without paying a real-world price. Were they to get their way, the consequences would be disastrous, above all for the planet’s poorest human beings, still mired in energy poverty, with all the misery it entails. A “fossil-free” future is a chimera, at least in our lifetime, and the divestment campaign can’t make things better by pretending otherwise. But don’t be surprised if it makes things worse.

(Jeff Jacoby is a columnist for The Boston Globe).