SACRAMENTO, Calif. - California voters will decide whether to legalize recreational marijuana use for adults, after the secretary of state on Wednesday certified the initiative for the November ballot.

It would become the first state to legalize recreational marijuana use if the proposition is approved. Marijuana use is legal for medicinal purposes in California and 14 other states, but the drug is illegal under federal law.

Secretary of State Debra Bowen certified that the petitions seeking to place the question on the ballot had more than 433,971 valid voter signatures, the minimum number needed to qualify.

If approved, the initiative would allow those 21 years and older to possess up to one ounce of marijuana, enough to roll several marijuana cigarettes. Residents also could cultivate the plant in limited quantities.

The proposal would ban users from ingesting marijuana in public or smoking it while minors are present. It also would make it illegal to possess the drug on school grounds or drive while under its influence.

Local governments would decide whether to permit and tax marijuana sales.

"The tide has turned," said Dan Newman, a strategist with the campaign backing the measure. "The combination of the broken budget and dysfunctional cannabis laws have created the perfect storm for this initiative to pass in November."

Opponents refer to marijuana as a gateway drug, meaning its use is believed to lead young people to try other, harder drugs. They worry that legalization would persuade more people to try it, worsening the nation's drug culture.

"How can our kids say no when the adults around them are saying yes?" asked Aimee Hendle, a spokeswoman for Californians for Drug Free Youth.

Proponents of the measure say legalizing marijuana could save the state $200 million a year by reducing public safety costs and could generate tax revenue for local governments.

Stephen Gutwillig, California director for the Drug Policy Alliance, said certification of the ballot initiative marks a watershed moment in the decades-long struggle.

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

The initiative is the second proposal to qualify for the November 2010 ballot. The other is a $11.1 billion water bond measure that was pushed by state lawmakers.