In the first significant challenge to California’s open cannabis market, 24 cities that restrict pot sales sued Gov. Gavin Newsom’s administration Thursday, arguing that by allowing home deliveries in their city limits, the state is violating 2016’s Proposition 64, which legalized recreational marijuana.

The lawsuit, which was filed in Fresno County Superior Court against the California Bureau of Cannabis Control and its chief, Lori Ajax, comes in response to a regulation adopted by the agency in January that permits state-licensed firms to deliver cannabis in cities that have banned pot shops. Officials from cities with prohibitions on pot sales objected to the rules, voicing concerns that home deliveries of cannabis would lead to robberies of cash-laden vans and an influx of illegal sellers blending in with licensed delivery fleets.