Adult Use of Marijuana Act: Prop. 64, California Law, Statutory initiative Summary of California’s new marijuana laws March 10, 2017 chrisconrad420 2 Comments Effective November 9, 2016: Here are California’s adult use marijuana laws Learn more about Proposition 64 by reviewing this link. These counties voted Yes on Proposition 64 View a chart showing county by county election returns. Prop. 64 results are on pages 74 – 76.