Top officials in 27 cities across the country are backing a lawsuit over the FCC’s repeal of net neutrality, claiming that removing those protections makes it more difficult for municipal governments to function.

“Government websites could be just as affected as your favorite movie streaming service if net neutrality comes to an end,” said Seattle City Attorney Pete Holmes in a statement.

New York, Seattle and other cities are asking the U.S. Court of Appeals for the D.C. Circuit to overturn the FCC’s 2017 vote to end net neutrality, a nickname for regulations that prevent internet providers from throttling service to customers or demanding pay for faster speeds.

“Internet service providers should not have the power to decide which services communities across the country can access online,” said Seattle Mayor Jenny Durkan in a statement.

Cities are concerned that internet providers could “delay government systems that rely on real-time transmissions to convey information to police and firefighters, issue emergency alert messages, and transmit payment of local taxes or registration for public benefits,” according to Durkan’s office.

That scenario isn’t hypothetical. Last week, a fire department in California said Verizon throttled service while they were fighting a massive wildfire, demanding the office pay to upgrade for double the cost in order to access faster speeds. Verizon said the incident was a customer service error and didn’t have anything to do with net neutrality, a claim the fire department disputes. Verizon said it will stop limiting speeds during emergencies going forward.

City officials are joining a chorus of voices seeking to influence Mozilla v. FCC and other net neutrality lawsuits in the form of amicus briefs. Mozilla is joined by Vimeo, Etsy, and other tech companies as plaintiffs in the lawsuit cities are backing. Oral arguments for that case have not been scheduled yet.

It’s one of many legal challenges to the FCC’s controversial decision to repeal net neutrality. Other companies, advocacy groups, and attorneys general from 22 states, including Washington, have also filed lawsuits. A coalition of trade groups that represent companies like Amazon, Facebook, and many others filed a brief supporting the states in their lawsuit earlier this week.

States are also mounting net neutrality defenses at the legislative level. Washington and Oregon passed laws preserving net neutrality principles for residents of those states. On Thursday, California’s state Assembly approved a bill that would create the toughest net neutrality standards in the nation. It now heads back to the state Senate for a vote.

The FCC anticipated these moves and included language that preempts states’ authority to pass their own net neutrality laws in the repeal. The 22 states suing the FCC are seeking to remove that mandate as part of their lawsuit.

“A free and open internet forms the backbone of the twenty-first century economy and allowing internet providers the ability to throttle or deny access to the internet contradicts the fundamental democratic principle of net neutrality,” Durkan said.