New York City Mayor Bill De Blasio announced the formation of “Mayors for Net Neutrality,” a coalition dedicated to preserving net neutrality, at a SXSW panel on Sunday. At time of writing, the coalition included 12 mayors in nine states, all pledging to protect net neutrality in response to the FCC’s recent repeal of existing internet regulations.

“The action taken by the FCC fundamentally affronts our democracy,” De Blasio said during the panel. “When you see the FCC undermine net neutrality, that’s a direct shot at public discourse and freedom of expression.”

De Blasio, joined onstage by Portland Mayor Ted Wheeler and Austin Mayor Steve Adler, argued that cities have the power and responsibility to help reinstate a free and open internet. At the municipal level, that translates not just to crafting legislation, but making politically motivated business decisions. “We will not do business with any internet service provider that does not honor net neutrality,” De Blasio said.

To join Mayors for Net Neutrality, De Blasio asked mayors across the nation to sign a pledge agreeing that they will only do business with internet service providers (ISPs) who uphold proponents of a free and open internet.

Their reasons aren’t purely ideological — De Blasio and his cohort fear that ISPs not beholden to net neutrality may throttle government-provided content, which has increasingly moved to the internet in recent years.

“Cities cannot allow private internet service providers to be the gatekeeper between our residents and the local government services on which they depend every day,” the pledge says.

The introduction of a new information gatekeeper is exactly what internet activists fear from net neutrality’s repeal, which is set to take effect April 23 unless Congress votes to strike down the FCC’s decision. Once it occurs, ISPs will have the freedom to privilege some types of content over others. That could mean establishing fast and slow lanes for different websites, or simply not offering access to certain sites as part of their service.

Given these concerns, the FCC repeal plan has been widely unpopular across the political spectrum. In fact, De Blasio and Mayors for Net Neutrality aren’t the first lawmakers attempting to defang the new FCC policy.

Last week, Washington became the first state to pass a bill re-establishing net neutrality within state limits. However, in their repeal plan, the FCC stipulated that local and state governments may not draft their own net neutrality policy, arguing that internet service crosses state lines. This means that the FCC could sue the state of Washington for breaking federal regulations.

Mayors pledged to defending net neutrality, on the other hand, aren’t vulnerable to legal action, because they aren’t enacting any specific regulations. However, what they lack in legislative authority they make up for with economic leverage. De Blasio estimated that NYC will pay out around $500 million dollars in ISP contracts in the next few years, and all that money will go to net neutral ISPs. To hear him tell it, that might be the most potent force in the battle for net neutrality.

“We’re gonna use our economic power to force the hands of these companies,” de Blasio said. “We’re gonna build a movement among other cities.”