The newly opened California chapter of a nonprofit using oil extracted from cannabis to treat children’s seizures and cancer will relocate because of Los Angeles’ crackdown on marijuana dispensaries.

Last week, Realm of Caring California, which operates a resource center in the San Fernando Valley received a letter from the city’s attorney threatening criminal charges if the nonprofit stays open. The notice came automatically as part of last year’s passage of Proposition D, which limits dispensaries to those approved in 2007.

“Everybody else has to shut down,” said Ray Mirzabegian, executive director of Realm of Caring California. “We don’t sell anything, this is a resource center. It is a place where I grow the plants, and it is a place where parents come to find out more information.”

At least 100 dispensaries have closed in Los Angeles since the law went into effect, according to prior statements by City Attorney Michael Feuer. A call to the City Attorney’s Office went unreturned Tuesday.

Realm of Caring’s popularity exploded in Colorado last year after families learned its marijuana strain — which does not produce a high — showed anecdotal success in reducing seizures in pediatric and adult patients.

The group uses a Colorado-created strain of medical marijuana called Charlotte’s Web, which was made in 2012 by the Stanley Brothers and contains high amounts of a compound called cannabidiol but very little THC, the driving force behind marijuana’s intoxication. The strain, named for first patient 5-year-old Charlotte Figi, dramatically reduced the child’s seizures from hundreds per week to two or three a month.

Realm of Caring California treats 26 families now but has more than 500 on the waiting list. Approximately 2,000 families exist on the list between California and Colorado, the only two states Realm of Caring operates in.

The letter forced Mirzabegian to shutter the resource center earlier this week after a year of work to get it started.

“We’re not going to jeopardize the medicine and the plants,” he said. “If they want us out of the city, that’s what we’re going to do.”

The nonprofit met with officials in Northern California on Monday and plans to reach out to cities east of Los Angeles — in the San Gabriel Valley and San Bernardino — to try to find a new home closer to their existing patients.

“It’s not going to affect the patients at this point,” Mirzabegian said. “It’s going to affect our budget. We invested a lot of money in that place.”