This chapter is subject to repeal or modification at the sole discretion of the city council; provided, that such repeal or modification shall apply prospectively only, and shall have no effect upon the obligation to indemnify and/or defend against any claim which is based, in whole or in part, upon any act or omission of an official occurring prior to the effective date of the repeal or modification. (Ord. 798 § 1, 1998).