California Code, Penal Code - PEN § 30905

(a) Except as provided in Section 30600, any person who lawfully possesses any .50 BMG rifle prior to January 1, 2005, that is not specified as an assault weapon under former Section 12276, as it reads in Section 19 of Chapter 606 of the Statutes of 1993, or former Section 12276.5, as it reads in Section 3 of Chapter 954 of the Statutes of 1991, or defined as an assault weapon pursuant to former Section 12276.1, as it reads in Section 3 of Chapter 911 of the Statutes of 2002, shall register the .50 BMG rifle with the department no later than April 30, 2006, pursuant to those procedures that the department may establish.

(b) The registration shall contain a description of the firearm that identifies it uniquely, including all identification marks, the full name, address, date of birth, and thumbprint of the owner, and any other information that the department may deem appropriate.

(c) The department may charge a fee for registration of twenty-five dollars ($25) per person to cover the actual processing and public education campaign costs of the department.  The fees shall be deposited into the Dealers' Record of Sale Special Account.  Data-processing costs associated with modifying the department's data system to accommodate .50 caliber BMG rifles shall not be paid from the Dealers' Record of Sale Special Account.