Cal. Elec. Code § 18103

Any person who knowingly or negligently (a) interferes with the prompt transfer of a completed affidavit of registration to the county elections official, (b) retains a voter’s completed registration card, without the voter’s authorization, for more than three days, excluding Saturdays, Sundays, and state holidays, or after the close of registration, or (c) denies a voter the right to return to the county elections official the voter’s own completed registration card, is guilty of a misdemeanor punishable by a fine not to exceed one thousand dollars ($1,000).