One must be at least 18 years of age to own/purchase a rifle or shotgun;

One must be at least 21 years of age to own/purchase a pistol-gripped shotgun or a handgun;

One who wishes to purchase any specially regulated device (such as a gun that can be fired in full-automatic mode) is subject to a special application, fingerprinting and background check, Federal tax, and must comply with many restrictions on its possession and use.

A non-Nevada resident can purchase a handgun here, but must have it shipped from an FFL dealer to an FFL dealer in your area.

Where there are State and/or local firearms regulations (i.e. waiting periods, permits to possess, training course requirements, etc.), those residents must comply with them before taking possession a firearm. In most cases, this means the firearm must first be shipped to a local FFL dealer where you live so that he can ensure you comply with those State and/or local regulations. In particular, this applies to all California residents.