The notion of turning a former gun store into a marijuana dispensary appeared quintessentially San Francisco, in a state that voted in 2016 to ban assault weapons and legalize recreational weed.

But after three years and mounds of paperwork, a project to replace a gun store with a cannabis retailer remains stalled. The would-be tenant has sued its landlords, a former partner and rival marijuana operator, alleging fraud and wrongful eviction. Though it has its own twists, the saga reflects the hurdles to opening a small business, particularly a pot shop, and how control of precious San Francisco real estate can erupt into litigation.

High Bridge Arms in the Outer Mission District was the city’s last gun store. It closed in fall 2015 after 63 years in business as more firearm sales regulations loomed and federal investigators contemplated revoking its license. The new medical marijuana dispensary was also to be called High Bridge.

But three years later, the building at 3185 Mission St. remains empty and locked, one of the many vacant storefronts dotting San Francisco neighborhoods.

The New Bernal Inc., a medical marijuana group, applied for a permit to operate in the former gun shop just months after it closed. The group was evicted from a nearby location, where it had operated as Bernal Heights Collective for a decade, after that building was sold in 2015. A more upscale dispensary called Harvest Off Mission replaced the collective.

Sean Killen, then-CEO of the New Bernal Inc., sued Harvest in 2016 in an effort to stay in the previous location, but later dropped the suit. “In the moment, we were emotional and defensive,” Killen told The Chronicle in January 2017. “We’re not going to oppose anyone. We’re just going to try to serve our patients.”

Killen said at a Planning Commission hearing that month that the former gun shop was an ideal location, just a couple blocks from its previous home. Thousands of customers, including seniors, disabled people and minority groups, would continue to be served, he said.

“Everyone is supportive and, in fact, somewhat frustrated that we haven’t managed to open back up again,” Killen said at the hearing.

The Planning Commission unanimously approved the dispensary.

But in the past year, the partnership behind the project has crumbled and there is now a battle for control of the property.

In October 2017, Killen’s company Steam Labs sued building owners Masashi and Margaret Takahashi for breach of contract, alleging that they failed to consent to the operation of a dispensary in the building, which is required for city approvals.

In June, Steam Labs Inc. filed a second lawsuit against Bret (spelled elsewhere as Brett) Todoroff, Sean DeVries and Humboldt Brothers LLC, alleging fraud, negligence and wrongful eviction. Steam Labs also amended its first lawsuit against the landlords to add those defendants and added similar charges.

DeVries was previously listed as the chief operating officer of New Bernal Inc. in city records, and Killen was listed as CEO.

Steam Labs signed a five-year lease at 3185 Mission St. in 2015, with monthly rent of $5,000, and sought to transfer the lease to New Bernal Inc., according to a San Francisco Department of Public Health application in 2016.

But Steam Labs “developed concerns about self-dealing” — that its partners were favoring their own interests — and ended its relationship with New Bernal Inc., according to a second lawsuit Steam Labs filed in June. Todoroff and DeVries allegedly worked with the Takahashis to push Steam Labs out of the building. The lawsuit says the Takahashis changed the building’s locks last year to block access to the building after Steam Labs had invested tens of thousands of dollars in renovations, and began collecting rent from DeVries in violation of the lease. The suit also alleged that the defendants inflated the value of the building to block Steam Labs from buying it.

Steam Labs is seeking monetary damages exceeding $25,000 and affirmation from the court that it has the rights to occupy the building and open a dispensary.

An attorney for the Takahashis said in a cross-complaint filed in January that Steam Labs’ allegations are not only false but that the company “was used as a criminal liability shield” for an “illegal cannabis delivery service.”

The cross-complaint alleges that Killen and Steam Labs partner Joseph Noble “burned several of their partners” at New Bernal Inc. and engaged in “theft” of all of the organization’s funds in June 2016. The next month, Killen and Noble allegedly began the unlicensed sale of cannabis from the Mission Street building and were issued a cease and desist from the health department, according to the cross-complaint. The cross-complaint also says Killen filed a meritless lawsuit that blocked the sale of the building.

The Takahashis are seeking punitive and general damages and compensation for attorney’s fees.

Masashi Takahashi, reached by phone, said he is unaware of the details of why Killen and DeVries’ partnership collapsed. “I don’t know about their business,” he said.

Takahashi said Killen sued in part because Takahashi’s wife didn’t respond to Killen’s phone calls. “Killen sues everybody,” he said.

Takahashi said DeVries has been paying rent. He said he wasn’t sure of the identities of the people involved in the most recent attempts to open a dispensary. The building’s restroom has been renovated, but the rest of the space is empty, Takahashi said.

Killen and his attorney, Vernon Goins, didn’t respond to requests for comment.

Humboldt Brothers operates marijuana farms in Humboldt County, according to its website. Michael Earls, chief operating officer of Humboldt Brothers, wrote in an email that he personally had “nothing to do with” the project and referred a request for comment to Todoroff, who did not respond. DeVries couldn’t be reached for comment.

Both Killen and Todoroff have separately sought approval for a medical dispensary from the health department, but neither of them has received it.

Killen’s initial application for New Bernal Inc. has yet to be heard and is at a “standstill,” said Veronica Vien, a spokeswoman for the health department.

In September 2017, HBSF Inc. applied to open the Humboldt Brothers dispensary in the space.

The Humboldt Brothers application was rejected by the Department of Public Health in June because “false documentation was knowingly provided to DPH in regards to who the property owner was in a lease,” Vien said. Humboldt Brothers appealed, and the Board of Appeals plans to hear the case on Oct. 25.

Humboldt Brothers’ application lists the building owner as 3185 Mission St. LLC, while the earlier New Bernal application lists the owner as “Mr. Takahashi.” Property records confirm that the Takahashis still own the building.

Both medical and recreational marijuana companies are “challenged by numerous things,” including state taxes and supply chain expenses, said Nicole Elliott, director of the city’s Office of Cannabis, which has coordinated approvals since recreational sales were legalized in California in January. Dispensaries could face more expenses, as San Francisco voters consider a new gross receipts tax on cannabis in November.

Historically, medical marijuana companies have taken one or two years to secure approvals, but the legalization of recreational marijuana has led to longer approval times as more operators apply, Elliott said.

Currently, 37 locations in San Francisco are permitted for medical marijuana sales, and there are 138 temporary permit holders that need further approvals. An additional 86 businesses have applications in process, according to Elliott. Some other applications, including the one at 3185 Mission St., predate the creation of the Office of Cannabis, she said.

While some neighborhoods have fought dispensaries, more retail businesses would be welcome in the Outer Mission area, which has many vacant storefronts, neighbors said. Eden Stein, president of Mission Bernal Merchants Association, said high rents, the cost of revamping interiors, and the challenge of obtaining city permits are among the barriers to businesses opening. A 2016 fire displaced multiple businesses and residents, including Cole Hardware. The corner, which is a few blocks from the former gun shop, has yet to recover. But new businesses are also arriving, such as Outer Orbit, a Hawaiian restaurant and pinball bar that opened Friday.

“We do have a lot of vacant storefronts, but people are starting to move into the neighborhood,” said Stein, who owns the gift shop and gallery Secession Art and Design. “A lot of them live here or have connections here.”

Longer leases would help retailers justify the costs of investing in new shops, said Stein, the gallery owner.

“Landlords really need to give you a five-year to 10-year opportunity, instead of a three- to five-year block,” she said.

On Mission Street, a faded, L-shaped “GUNS” sign still hangs above the High Bridge site. The five-year lease is halfway through. And nothing is for sale.

Roland Li is a San Francisco Chronicle staff writer. Email: roland.li@sfchronicle.com Twitter: @rolandlisf