LOS ANGELES (Reuters) - A California voter initiative that would legalize possession and sale of marijuana has qualified for the November ballot, state election officials said on Wednesday, in what supporters called a “watershed moment” for their cause.

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Passage of the measure, by no means certain, would make California the first U.S. state to legalize marijuana. Backers believe the state could be at the vanguard of a national movement toward decriminalizing the drug.

“This is a watershed moment in the decades-long struggle to end marijuana prohibition in this country,” said Stephen Gutwillig, California director of the Drug Policy Alliance, which has spearheaded the ballot initiative.

“Banning marijuana outright has been a disaster, fueling a massive, increasingly brutal underground economy, wasting billions in scarce law enforcement resources and making criminals out of countless law-abiding citizens,” he said.

California Secretary of State Debra Bowen said in a written statement that her office had certified the measure for the November 2 general election ballot after backers submitted the required number of signatures on petitions.

Bowen said that proponents, who needed 433,971 valid signatures to qualify for the ballot, had submitted 694,248 that were verified through a random sampling.

POLLS SHOW MANY SUPPORT MEASURE

Legalizing marijuana appears to have broad support in the state, with some 56 percent of Californians surveyed in an April, 2009 Field Poll saying they favored making it legal for social use and taxing the sales proceeds.

In October, Gallup found 44 percent of Americans favored legalization.

Activists have suggested that taxing marijuana sales could help bail out the cash-strapped state, but plenty of Californians still oppose marijuana.

“With legalization of recreational marijuana use, impaired driving, fatalities, injuries and crashes will go up, and we don’t want to see that,” California Mothers Against Drunk Driving spokesman Silas Miers said.

The measure’s qualification for the ballot was “the first step toward its defeat,” said John Lovell, a lobbyist who represents a number of law enforcement groups.

Critics also say the social costs of a free-smoking state far outweigh the money it would bring in.

They say that the already enormous societal damage from alcohol and tobacco use would only increase if people were allowed to legally sell and smoke pot.

Under the initiative, simple possession of an ounce (28.5 grams) or less of marijuana, currently a misdemeanor offense punishable by a $100 fine, would be legal for anyone at least 21. It also would be lawful to grow limited amounts in one’s own home for personal use.

While sales would not be legalized outright, cities and counties could pass laws permitting commercial distribution subject to local regulations and taxes. Retail sales would still be limited to an ounce for adults 21 and older.