California Vehicle Code Section 39002 Bicycle License Requirement
39002. (a) A city or county, which adopts a bicycle licensing ordinance or resolution, may provide in the ordinance or resolution that no resident shall operate any bicycle, as specified in the ordinance, on any street, road, highway, or other public property within the jurisdiction of the city or county, as the case may be, unless the bicycle is licensed in accordance with this division.
(b) It is unlawful for any person to tamper with, destroy, mutilate, or alter any license indicia or registration form, or to remove, alter, or mutilate the serial number, or the identifying marks of a licensing agency's identifying symbol, on any bicycle frame licensed under this division.
... Basically, the state leaves the right & authority to license bicycles to local jurisdictions. Although the majority of Californians live in areas where California bicycle licenses are offered or even mandated by local authorities, participation in these programs is not widespread across the state.
BUT.. some governmental agencies are exploiting the 'up to local agencies' requirement to squeeze fees from unsuspecting people, case in point:
http://daviswiki.org/Bicycle_License
"Section 6.02. Impounding of Unlicensed Bicycles. The Police Department and Transportation and
Parking Services are authorized to impound unlicensed bicycles or bicycles with expired licenses and
remove them to an area designated for storage. Bicycles so impounded may be recovered only upon
proof of ownership and after required fees are paid. No bicycle shall be released unless it is licensed in
accordance with Section 6.01. Unclaimed bicycles, which have been impounded because they were
unlicensed or impounded for violation of parking regulations set forth in this Code, shall be held for a
minimum of 90 days at which time the owners shall be presumed to have relinquished their legal title.
Such bicycles shall be sold at public auction without reserve. The same disposition shall be applied to
bicycles which remain unclaimed after storage with the Police Department or Transportation and
Parking Services and to stolen bicycles which have been recovered by the Police Department if said
bicycles remain unclaimed for a period of 90 days. Notices will be sent as soon as practicable
whenever possible to the owners of all bicycles removed to a storage area."
Anyways, getting back to my original quest, which was to help decipher bike license plates, as I collect them.