California Code, Public Utilities Code - PUC § 130533

(a) Except as provided in this subdivision and as may be otherwise expressly provided by the commission, all issues of its bonds are special obligations of the commission payable from any revenues or money of the commission available therefor and not otherwise pledged, subject only to any agreement with the holders of particular bonds pledging any particular revenues or money. However, the commission may not pledge revenues or money from the following sources: federal funds provided under Sections 1602 and 1607a of Title 49 of the United States Code,  1 funds allocated pursuant to subdivisions (a) and (b) of Section 99312 from a state transit assistance fund created pursuant to Section 99313.6, funds allocated from the Transportation Planning and Development Account in the State Transportation Fund, funds subject to Article XIX of the California Constitution, and funds provided pursuant to the Mills-Alquist-Deddeh Act (Chapter 4 (commencing with Section 99200) of Part 11 of Division 10).

(b) The commission may not pledge any of its revenue derived from the retail transactions and use tax which have been allocated to a city pursuant to the ordinance adopted pursuant to Section 130350, unless the city has authorized the pledging of its allocation.

(c) Notwithstanding that the bonds may be payable from a special fund, they are for all purposes negotiable instruments, subject only to the provisions of the bonds for registration.