California cannot declare bankruptcy.
The legal definition of municipality needs tested: "Only a "municipality" may file for relief under chapter 9. 11 U.S.C. § 109(c). The term "municipality" is defined in the Bankruptcy Code as a "political subdivision or public agency or instrumentality of a State." 11 U.S.C. § 101(40). The definition is broad enough to include cities, counties, townships, school districts, and public improvement districts. It also includes revenue-producing bodies that provide services which are paid for by users rather than by general taxes, such as bridge authorities, highway authorities, and gas authorities.
http://www.uscourts.gov/bankruptcycourts/bankruptcybasics/chapter9.html