California Code, Public Resources Code - PRC § 5590

The bonds of any district issued pursuant to this article, are legal investments for all trust funds, and for the funds of all insurance companies, banks, both commercial and savings, and trust companies, and for the State school funds;  and whenever any money or funds may by law be invested in bonds of cities, cities and counties, counties, or school districts in the State of California, such money or funds may be invested in district bonds issued in accordance with the provisions of this article;  and whenever bonds of cities, cities and counties, counties, school districts, or municipalities may by law be used as security for the performance of any act, district bonds may be so used.