As the most populous state in the Union and home to an economy that would rank number five in the world if it was its own country, California is the biggest prize in the legal US sports betting industry. Legal sports betting will likely come to California at some point, but what form it will take remains uncertain. Each maintains a physical presence in the US, which means they are all subject to state and federal law. The above betting sites are open to customers from California. 2023-2024 California Sports Betting Proposals.