CAL. GOV. CODE § 6500
As used in this article, “public agency” includes, but is not limited to, the federal government or any federal department or agency, this state, another state or any state department or agency, a county, county board of education, county superintendent of schools, city, public corporation, public district, regional transportation commission of this state or another state, a federally recognized Indian tribe, or any joint powers authority formed pursuant to this article by any of these agencies.
CAL. GOV. CODE §6502
If authorized by their legislative or other governing bodies, two or more public agencies by agreement may jointly exercise any power common to the contracting parties, even though one or more of the contracting agencies may be located outside this state. It shall not be necessary that any power common to the contracting parties be exercisable by each such contracting party with respect to the geographical area in which such power is to be jointly exercised….