Californians will decide in November whether to legalize marijuana for recreational purposes, after a measure backed by Lt. Gov. Gavin Newsom and Facebook investor Sean Parker gathered enough signatures to qualify for placement on the state ballot this fall.

California Secretary of State Alex Padilla announced Tuesday that the Control, Regulate and Tax Adult Use of Marijuana measure had collected more than 600,000 signatures — far more than the required 365,880 signatures needed for its placement on the November 8 ballot.

If approved by California voters, the measure would fully legalize marijuana and hemp in the state and would place a 15 percent sales tax on its sale, as well as a cultivation tax of $9.25 per ounce for flowers and $2.75 per ounce for leaves. State residents would be allowed to possess and use up to an ounce of marijuana and could grow up to six plants for personal use.

Medical marijuana would be allowed some tax exemptions.

“Today marks a fresh start for California as we prepare to replace the costly, harmful and ineffective system of prohibition with a safe, legal and responsible adult-use marijuana system that gets it right and completely pays for itself,” measure spokesman Jason Kinney said in a statement.

The measure received heavy financial support from Parker, who contributed more than $1 million to the effort. Other significant backers include the George Soros-supported Drug Policy Action organization, and CA for Sensible Reform, which contributed $750,000 and is primarily funded by marijuana dispensary-finding website Weedmaps.

In all, the measure’s supporters have raised approximately $3.7 million, according to the Los Angeles Times.

The measure’s opponents, comprised of law enforcement groups —  including the California Police Chiefs Association and the California State Sheriff’s Association under a broader outfit called the Coalition for Responsible Drug Policies — have raised just $125,000 to date, the Times reported.

Law enforcement groups say the 2016 measure contains several potentially harmful provisions, including allowing convicted felons to obtain licenses to cultivate and sell marijuana.

A similar measure that would have legalized marijuana for recreational use, Proposition 19, failed to pass in 2010, with 53% of California voters voting against it.

Recent polling, however, suggests that the measure will pass this year. A poll conducted in February 2016 by Probolsky Research found that 59.9 percent of likely California voters would support the measure, while just 36.7 percent would vote against it. The poll was conducted among 1,000 registered California voters and had a 3.1 percent margin of error.

Follow Daniel Nussbaum on Twitter: @dznussbaum