If you want alcohol at your event, California law requires strict compliance. Here's what you need to know:

• No license is needed if your event is invite-only, alcohol is host-provided, guests pay nothing for drinks, and there is no entry fee
• If alcohol is sold in any form, you'll need a permit:
  • ABC 221 Daily License — nonprofits and qualified organizations only
  • ABC 218 Special Event Permit — requires hiring a licensed caterer to apply
• Certified (RBS) bartenders are always recommended

More details here.