Penal Code § 30400
ARTICLE 1. Restrictions Relating to Firearm Precursor Parts
(a) Except as provided in subdivision (b) and in Section 30420, or except by operation of law, it shall be unlawful for a person to purchase, sell, offer to sell, or transfer ownership of any firearm precursor part in this state that is not a federally regulated firearm precursor part.
(b) This section does not apply to either of the following:
(1) The purchase of a firearm precursor part that is not a federally regulated firearm precursor part by a federally licensed firearms manufacturer or importer, or by a federal licensee authorized to serialize firearms.
(2) The sale, offer to sell, or transfer of ownership of a firearm precursor part that is not a federally regulated firearm precursor part to a federally licensed firearms manufacturer or importer, or to a federal licensee authorized to serialize firearms.
(c) A violation of this section is a misdemeanor punishable by imprisonment in a county jail not exceeding six months, by a fine not exceeding one thousand dollars ($1,000), or by both that fine and imprisonment.