To begin with, all online casinos must be licensed by the California Gambling Control Commission (CGCC). This means that you need to obtain permits for any gaming activities you plan to offer. The process can be complicated and time-consuming, so it's best to hire a lawyer who specializes in this area of law.
The Unlawful Internet Gambling Enforcement Act of 2006 makes it illegal to operate an online gambling website anywhere in the US. But, it doesn't make it illegal for individuals to place wagers on an online gambling website.