California Code, Streets and Highways Code - SHC § 31162

Whenever bonds of any kind have been issued and are outstanding pursuant to this chapter, the authority may from time to time or at one time issue and sell or exchange funding or refunding bonds for the purpose of retiring, paying, funding, or refunding either all or such part of the outstanding bonds or of one or more issues or series thereof, as it deems advisable.  Such funding or refunding bonds shall be issued and delivered only when the issue or series of bonds to be funded or refunded have matured, are about to mature, are subject to retirement before maturity, or if the outstanding bonds are not subject to retirement, the retirement thereof has been assured or obtained by consent of the holders thereof.  Funding or refunding bonds may be delivered wholly or in part in exchange for outstanding bonds to be funded or refunded thereby, if the holders of the outstanding bonds to be exchanged consent thereto.