California Code, Penal Code - PEN § 30670

(a) Section 30600 shall not apply to the importation into this state of an assault weapon or a .50 BMG rifle by the registered owner of that assault weapon or a .50 BMG rifle if it is in accordance with the provisions of Section 30945.

(b) Section 30600 shall not apply during the first 180 days of the 2005 calendar year to the importation into this state of a .50 BMG rifle by a person who lawfully possessed that .50 BMG rifle in this state prior to January 1, 2005.