Cal. Pub. Util. Code § 90020

It is hereby declared to be the policy of the State of California to develop transit system districts in the various metropolitan areas within the state for the benefit of the people. A necessity exists within San Diego County for such a system. Because there is no general law under which this district could perform this distinct function, only a specially created district can operate effectively in the San Diego metropolitan area. Because of the unique problem presented by that metropolitan area, the adoption of a special act and the creation of a special district is required.