A unit of insurer MBIA Inc. challenged Stockton, Calif.'s, bankruptcy on Wednesday, saying that the case was invalid because the city did not first negotiate with its biggest unsecured creditor, the California Public Employees' Retirement System, Reuters reported yesterday. The National Public Finance Guarantee Corp., which insured nearly $94 million of the city's revenue bonds, said that the city was required to negotiate in good faith with creditors before filing, according to the objection filed in bankruptcy court.
