The California rule was common law ruling which implied all public sector contracts implicitly guarantee the pension promises for entire work period of the employee, certain parts of the employment contract being defined, by law, for an indefinite period.
Wages may be determined by fixed period contracts, partial vesting is recognized, but the pension promises must continue. On what basis? Generally understood verbal law. Actually it was white speaking english and little browns spanish, bu that is another story/. In any event we accept a verbal contract between government and unions.
From what basis did the quesion system get this guarantee? Out of state law, the Dills act mandating unions. But, Jerry and the little brown figured it out and modified the law, he new law changed future pension rules.
Which is correct? Does the legislature have sovereignty to change the Dills Act? Maybe not, we have states rights to do with as we polease, but it is not clear what we pleased. There is every bit of evidence that Jerry and the DIll Act was permanent vote to remove state democracy. Who is to rule differently? Who says we have not become a sort of union run government, on a permanent constitutional basis? Our only previous law was the Franciscan bible.