Unlike some other states, California gun law requires that all private party gun transfers be brokered through a licensed California gun dealer. If you don't participate in this type of required exchange, the circumstances of the offense will dictate which California gun law(s) prosecutors will accuse you of violating.
Penal Code 12070 PC California's law against the unlicensed sale of firearms, selling dangerous firearms prohibited under Penal Code 12020 PC, or Penal Code 12021 PC California's “felon with a firearm” law are a sample of some of the most common offenses that could be charged in connection with the unlicensed sale of a firearm.
It's important to understand the laws of the state in which you possess, purchase, or sell firearms. Each state has very different laws and each is independent of each other. The fact that it is okay to sell your gun at a garage sale in one state doesn't mean that this type of transaction will be legal in another.
Before engaging in any firearm transaction, it is a good idea to check with your local attorney general about your state's rules and regulations. Also read our article about California Safe Storage Gun Laws.