The Wizarding World of Harry Potter’s Diagon Alley. (Photo by Sheri Lowen/Universal Orlando Resort via Getty Images)

Right before Christmas, Warner Bros. quietly gave “Harry Potter” fans what was, for some of them, a long-wished-for gift. In a letter to Andrew Slack, the founder of the Harry Potter Alliance, Joshua Berger, the company’s president for Harry Potter Global Franchise Development, announced, “By the end of 2015, and sooner when possible, all Harry Potter chocolate products sold at Warner Bros. outlets and through our licensed partners will be 100-percent UTZ or Fair Trade certified.”

It’s the sort of victory that, in the past, might have been the result of a pressure campaign by trade advocates or union groups, employing the language of globalization and living wages. But Warner Bros.’ commitment to new standards for cocoa production grew out of pressure from and dialogue with “Harry Potter” devotees who wanted to see the franchise live up to the ideals their fictional hero fought for. The win comes after four years of organizing. And it’s a fascinating symbol of what activism might look like when it’s animated by fiction rather than political parties and when fans form coalitions with devoted advocates.

When Slack and his co-creators founded the Harry Potter Alliance in 2005, they were animated by the idea that J.K. Rowling’s novels, inspired both by her own experiences with poverty and her work at Amnesty International, could be a powerful source of moral precepts and ideas about how to build a more just world. They made videos about Walmart, comparing the corporation to Voldemort, the “Harry Potter” novels’ totalitarian villain, and started a large book drive. But over time their ambitions grew, applying a similar approach to Suzanne Collins’s dystopian exploration of inequality, “The Hunger Games,” and considering how alliance members might be convinced to move from what Slack refers to as “charity and acts of service” to more direct advocacy.

“It’s all well and good to send the silver parachutes,” Slack told me in an interview last week, referring to the care packages that “Hunger Games” characters can send participants during televised fights to the death, “But the Games are still the Games.”

The perfect opportunity presented itself when Slack met Lisa Valdez, an advocate who started educating him about labor abuses, particularly of enslaved children, in cocoa production.

Chocolate and candy play an important role in the “Harry Potter” books. After he leaves his abusive aunt and uncle to attend the Hogwarts School of Witchcraft and Wizardry, Harry is boggled by the abundance of sweets his peers have access to; chocolate is a symbol of how Hogwarts will be the first place that really nourishes Harry’s body and his mind. And chocolate is big real-world business in the “Harry Potter” empire: You can buy Chocolate Frogs, one of the series’ signature sweets.

The chance to turn fans into advocates by asking them to turn their energies into bettering the corporate practices of a franchise — Warner Bros. holds the merchandising rights to the Potter series — appealed to Slack.

“If ‘Harry Potter’ [as a franchise] were to be in alignment with the values of Harry Potter [himself], it could be a real symbolic and coherent victory,” Slack said. ” ‘Harry Potter,’ more and more, is becoming a classic, and one that children are growing up on, with all seven books having been written. It’s part of the culture. It represents righteousness, nobility, love, so much beauty and a place of safety that people go to, and moral authority. If the ‘Harry Potter’ brand were to move something like fair trade, it would be making a statement that not only is the ‘Harry Potter’ brand a cut above the rest but that [other franchises] have to catch up to it.”

The Harry Potter Alliance launched its cocoa campaign on Halloween in 2010 with the help of the author John Green, asking fans to ask Warner Bros. to meet high standards for its chocolate production. After the company sent the alliance its sourcing guidelines, the anti-slavery organization Free 2 Work reviewed the practices of the supplier for the chocolate sold at the Wizarding World of Harry Potter, Universal Parks & Resorts’ themed area. Free 2 Work gave the company an F, largely because transparency issues prevented auditors from determining if the producers met Warner Bros.’ stated standards.

When Warner Bros. took time to follow up on the report, the Harry Potter Alliance started organizing members in conjunction with another anti-slavery group, Walk Free, to petition the company to be open about its findings and to record videos called Howlers (borrowed from the magical scoldings in Rowling’s books), shaming the company for its pace. They got in touch with Rowling’s lawyer, who made inquiries. Walk Free even had a plan to loft a Dark Mark (a sign of Voldemort’s followers) over Warner Bros.’ studio facilities.

The pressure worked. And as advocacy campaigns go, this one has ended rather amicably, with Warner Bros. thanking the Harry Potter Alliance for “your partnership throughout our discussions on this important issue,” and Slack and Walk Free both emphasizing their praise for the company. (I spoke with a Warner Bros. representative off the record, but the company referred me to the letter as its public statement on the campaign and the change.)

One reason for the outcome might have been that the parties had shared interests. Like Warner Bros., the Harry Potter Alliance wants to keep J.K. Rowling’s creation in good standing. And like the alliance, Walk Free has an interest in finding new ways to spread messages about social justice and inequality.

“It wasn’t really a stretch at all,” Olly Buston, the movement director for Walk Free, wrote in an e-mail. “Harry Potter fans have spoken up and said they are opposed to modern slavery. So of course we want to work with them.” And he suggested that Harry Potter fans made for a powerful constituency because they were committed — and because Warner Bros. “can’t ignore the concerns of a key stakeholder group” the way the company might have been able to brush off an outside advocacy organization.

Henry Jenkins, a professor of communication, journalism, cinematic arts and education at the University of Southern California, says that the Harry Potter Alliance (which he has studied) is not alone in developing messaging tools that can be adapted to any number of causes, rather than identifying campaigns and then developing strategies for them.

“In some ways, the flexibility of what the Harry Potter Alliance is doing is very useful,” he suggested. “It can form new kinds of alliances, it can again evolve over time as the cultural references change. We could compare that to Occupy, which has an equally incoherent frame but has a simple message that it’s translated into dozens of different languages that travel differently across the country. … [In politics right now], what we’re seeing very little of is things like Marxism, which has a very overarching frame that it pursues no matter what. Compared to that kind of grand narrative, very little contemporary politics reacts in that way. It’s tactical, it’s situational, it’s responding to conditions on the ground. ‘Black Lives Matter’ is a slogan that has a certain power and coherence, but at the moment it’s been very closely focused on local events.”

And while the Harry Potter Alliance may continue to figure out how to motivate its fans to get involved involved in activism, activist organizations are starting to adopt similar tactics and rhetoric. Superman, who is technically an undocumented immigrant, became a symbol in the push for the Dream Act in 2010. The Harry Potter Alliance may not yet be a major force in voter registration or legislation-based advocacy, but Jenkins suggests that they and similar groups have another role.

“The idea of civic imagination is, before we can change the world, we have to imagine what a better world would look like, we have to imagine ourselves as political agents,” Jenkins argued. “I would say is what the Harry Potter Alliance does very well is foster the cultural imagination.”

The alliance also serves as a kind of force magnifier for Rowling herself. She is politically active, donating to the fight against Scottish independence and slapping back against media mogul Rupert Murdoch on Twitter over his suggestion that Muslims take collective responsibility for the murder of Charlie Hebdo staff and Paris police officers. If, as Slack suggested, the Harry Potter Alliance views Rowling as its Albus Dumbledore, the headmaster of Hogwarts, a figure who provides them with principles but leaves them to act for themselves, the alliance gives her a constituency that many wealthy figures lack, making her a movement leader without the day-to-day responsibility foisted on most people in that position.

“I can confirm that J.K. Rowling is delighted that Warner Bros. and Universal are taking positive steps to source only certified cocoa for Harry Potter chocolate,” Rowling’s publicist, Mark Hutchinson, wrote in an e-mail to me.

Walk Free and the Harry Potter Alliance both have to figure out what’s next. For Walk Free, it’s designing and propagating a new certification for slavery-free supply chains. Slack hopes to use Warner Bros.’ decision to pressure other chocolate chains, such as Hershey and Nestle, and mobilize fans of other franchises. But just as Dumbledore’s victory went beyond defeating Voldemort to educating the students who would do that work and then go on to make the wizarding world a better place, the cocoa campaign proves that the impact of Rowling’s novels isn’t limited to the pleasure it gives readers, or to a win in a single campaign for more ethical chocolate.