It is illegal to buy a gun in a different state and bring it to CA. Unless you have a C&R FFL. Edit - You can't buy, move, transport, nothing. It has to go through a registration process. No bringing guns across state lines. You can transport, though: https://oag.ca.gov/firearms/travel https://oag.ca.gov/firearms https://www.shouselaw.com/ca/defense/gun-laws/transporting-firearms/