Cal. Penal Code § 290.015
(a) A person who is subject to the Act shall register, or reregister if he or she has previously registered, upon release from incarceration, placement, commitment, or release on probation pursuant to subdivision (b) of Section 290. This section shall not apply to a person who is incarcerated for less than 30 days if he or she has registered as required by the Act, he or she returns after incarceration to the last registered address, and the annual update of registration that is required to occur within five working days of his or her birthday, pursuant to subdivision (a) of Section 290.012, did not fall within that incarceration period. The registration shall consist of all of the following:
(c)
(2) If the person was not on parole or probation or on postrelease community supervision or mandatory supervision at the time of release, the district attorney in the following applicable jurisdiction shall have the authority to prosecute that person pursuant to Section 290.018: