California Code, Government Code - GOV § 25486

Whenever the county advertises for bids for the furnishing of personal property, it may permit any person to submit at the time bids are received an offer of purchase of any county personal property designated in the notice and not further required for public use. It may permit or require the bidder to submit an offer of trade-in allowance. The offer of a bidder shall be considered in determining the lowest bid and is not binding upon him unless his bid is accepted. The county may reject all offers if it is to the advantage of the county to do so, and bidders will be bound by their bids.