Gwinnett County formally took a stand Thursday against the new city of Mulberry by asking to join a resident’s lawsuit seeking a declaration that the city, which voters approved in a May referendum, is unconstitutional.

“The City of Mulberry should not be allowed to come into being,” the county said in a Thursday filing in Fulton County Superior Court.

State House Majority Leader Chuck Efstration, a Republican who lives in the Mulberry borders, and Sen. Clint Dixon, a Republican whose district includes the new city, proposed it as a means to exert more local control over zoning in response to a proposal for hundreds of apartments in the area, which currently has no multifamily housing.

Their legislation, Senate Bill 333, included a charter stating that the new city could not impose a property tax and would provide zoning, code enforcement and stormwater services. The charter states that it can only be changed through another voter referendum. The bill passed and Gov. Brian Kemp signed it, sending the charter to voters, who ratified it in May.

State law precluded the county from taking a position on the ballot measure before the vote, but Gwinnett officials commissioned Valdosta State University to conduct a study that challenged a fiscal impact study Efstration commissioned. The county also said that the state constitution grants city councils the right to levy property taxes if they so choose.

Now, the county is saying so in court.

“I feel vindicated,” said Stephen Hughes, the retiree who has filed multiple lawsuits in Fulton and Gwinnett courts to overturn the new city. “To have Gwinnett County come in and agree with me, it makes me feel a whole lot better.”

Hughes last month sued the state of Georgia in Fulton County Superior Court, seeking a declaration that the law proposing Mulberry is unconstitutional and an injunction to stop Kemp from appointing a transition team for the new city. He had already sued Gwinnett County and Gwinnett elections officials in Gwinnett Superior Court, seeking to halt the transition and Mulberry city council elections scheduled for November.

In Fulton County court filings, Gwinnett County said it didn’t want to pay for city council elections or a transition process for a city with an unconstitutional charter.

“Gwinnett County is placed underneath a sword of Damocles,” the motion said.

The city will reimburse the county for the cost of the elections, said Michael Coker, president of the pro-cityhood group Citizens for Mulberry. The group is not a party in the Fulton court case but Coker said he would consider intervening in it.

He said Gwinnett’s legal complaint was indicative of complaints against the county that led voters to approve Mulberry.

“This is the kind of stuff that we have to deal with, unfortunately,” Coker said. “It’s just another indication they want to maintain control of the area.”

The county’s complaint also contains screengrabs of the pro-cityhood campaign’s website, which promises no city property tax. Voters approved the city based on that information and taking it out of the charter while keeping the city would be a “bait and switch” to voters, the county said.

Spokespersons for Gwinnett County and Attorney General Chris Carr declined Friday to comment, citing policies against commenting on pending litigation.

Mulberry encompasses 26 square miles and about 41,000 residents in northeastern Gwinnett. It is scheduled for incorporation Jan. 1 when its first city council is sworn in. It would be Gwinnett’s largest city by land area and second-largest by population. Its residents are wealthier, whiter and more Republican than the county as a whole, according to state and federal data.