LOS ANGELES — In the heart of Northern California's marijuana growing region, the Sheriff's Office is inundated each fall with complaints about the stench of marijuana plots or the latest expropriation of public land by growers.
The area's tranquil communities have been altered by the emergence of a wealthy class of marijuana entrepreneurs, while nearly 500 miles away in Los Angeles, officials have struggled to regulate an explosion of medical marijuana shops.
But at a time when polls show widening public support for legalizing marijuana — recreational marijuana is about to become legal in Colorado and Washington state , and voter initiatives are in the pipeline in at least three others states — California's 17-year experience as the first state to legalize medical marijuana offers surprising lessons, experts say.
Warnings voiced against partial legalization — of civic disorder, increased lawlessness and a drastic rise in other drug use — have proved unfounded.
Instead, research suggests both that marijuana has become an alcohol substitute for younger people here and in other states that have legalized medical marijuana, and that while driving under the influence of any intoxicant is dangerous, driving after smoking marijuana is less dangerous than after drinking alcohol.
Although marijuana is legal in California only for medical use, it is widely available. There is no evidence that its use by teenagers has risen since the 1996 legalization, though it is an open question whether outright legalization would make the drug that much easier for young people to get, and thus contribute to increased use.
And though Los Angeles has struggled to regulate marijuana dispensaries, with neighborhoods upset at their sheer number, the threat of unsavory street traffic and the stigma of marijuana shops on the corner, communities that imposed early and strict regulations on their operations have not experienced such disruption.
Imposing a local tax on medical marijuana, as Oakland, San Jose and other communities have done, has not pushed consumers to drug dealers as some analysts expected. Presumably that is because it is so easy to get reliable and high-quality marijuana legally.
Finally, for consumers, the era of legalized medical marijuana has meant an expanded market and often cheaper prices. Buyers gaze over showcases offering a rich assortment of marijuana, promising different potencies and different kinds of highs.
Advocates for marijuana legalization see the moves in Colorado and Washington as the start of a wave. A Gallup poll released last week found that 58 percent of Americans think the drug should be made legal.
"There is definitely going to be a legalization here at some point, one way or another, like in Colorado and Washington," said Tom Ammiano, a Democratic state assemblyman from San Francisco who has pushed the Legislature to legalize recreational marijuana use.
Still, even as public opinion in support of legalizing marijuana has grown, opposition remains strong among many, including some law enforcement organizations, which warn that the use of the drug leads to marijuana dependence, endangers the health of users, and encourages the use of other drugs.
After California, medical marijuana was legalized in 19 states and the District of Columbia, according to the National Conference of State Legislatures.