Timeline: California Online Gambling Law History Online Gambling Licensing Fee: To Be Determined.Licensed Sports Betting Operators: None.Estimated Sports Betting Revenue: To Be Determined.Minimum Gambling Age in California: 21 (domestic), 18 (through offshore sites).Legal Gambling: Land-Based Casino (domestic), Online/Mobile Casino (offshore).How to Gamble Online in the United States.The Best California Online Casino Sites List 2023.