california ballot measureshttps://ballotpedia.org/Laws_governing_the_initiative_process_in_California
California ballot measures require only a simply majority of the votes cast for or against them.
See law:California Constitution, Article II, Section 10 (a)
Effective date
In California, approved measures take effect on the day after the election unless otherwise specified by the measure.
See law:California Constitution, Article II, Section 10 (a)
full measure: https://www.oag.ca.gov/system/files/initiatives/pdfs/15-0103%20(Marijuana)_1.pdf?