LOS ANGELES, Calif. – Letters will be sent this week to the operators of at least 400 medical marijuana dispensaries in Los Angeles, ordering them to close by June 7.

“It will inform (operators) that a new ordinance is going into effect, and it is our understanding that their establishment is operating outside compliance and will be required to shut down,” said Frank Mateljan, a spokesman for the City Attorney’s Office. The letters will be sent soon, he said.

The ordinance that takes effect June 7 allows up to 186 dispensaries to remain open–those that started before the City Council instituted a moratorium on Nov. 13, 2007.

The ordinance, which Mayor Antonio Villaraigosa signed last week, states that “any existing medical marijuana collective, dispensary, operator, establishment or provider that does not comply with the requirements of this article must immediately cease operation.”

Mateljan said the City Attorney’s Office has prepared an initial list of about 400 operators that opened dispensaries after the moratorium was put in place. If they have not shut down of their own volition by June 7, the city will force them to do so, he said. Dispensaries that opened prior to the moratorium will be required to file a notice of intent to register with the City Clerk’s Office and will be put on a priority list.

The ordinance requires dispensaries to be at least 1,000 feet away from schools, public parks, public libraries and religious institutions, as well as each other. It also bars dispensaries from being “on a lot abutting, across the street or alley from, or having a common corner with a residentially zoned lot or a lot improved with residential use.”

If two dispensaries are within 1,000 feet of each other, the City Clerk’s Office will use the priority list to determine which one can stay.

There were 186 dispensaries that opened prior to the moratorium, and about 130 are believed to still be operating, city officials said. Some operators of medical marijuana dispensaries have said they plan to challenge the ordinance in court, on the grounds that it will effectively zone dispensaries out of existence.