CONCORD -- Despite pleas from medical marijuana users, the City Council voted unanimously Tuesday to ban outdoor cultivation of medical marijuana.

Council members acknowledged the medical benefits of marijuana for patients but said the risks outdoor grow operations pose to public safety -- such as robbery -- were too great.

"It's up to the council to do a balancing act and weigh what is good for all in the community," said Councilman Ron Leone. "My chief concern that I have is safety."

The ban, which is modeled after an ordinance used in Moraga, restricts the growing of medical marijuana to occupied housing units, and expands the city's regulation of pot. In 2005, council approved a ban on medical marijuana dispensaries.

City Attorney Mark Coon, who recommended the ban, said the city would begin enforcing it in two to three months after warning people who currently grow medical marijuana in their backyards. The ban will be enforced by city code enforcement officers responding to citizen complaints.

The issue was first brought to the council last year, when a resident in the Dana Estates neighborhood complained about a neighbor growing pot in his backyard. That neighbor, Chris Olsen, said Tuesday he plans to file a lawsuit against the city.

All but one of the 13 residents who spoke at the meeting asked the council to reconsider the ordinance. Several residents told members they have grown medical marijuana in their backyards without any trouble, and have followed state law.

State voters decriminalized medical marijuana for qualified patients and caregivers with the passage of The Compassionate Use Act in 1996, though using or growing pot remains a crime under federal law.

"It's a solution for a problem that doesn't exist," said Wendy Hershey.

David DeBolt covers Concord and Clayton. Contact him at 925-943-8048. Follow him at Twitter.com/daviddebolt.