427B.22  Credit may be repealed.
  If in the opinion of the city council or the county board of supervisors continuation of the credit granted under an ordinance adopted pursuant to this division ceases to be of benefit to the city or county, the city council or the county board of supervisors may repeal the ordinance authorized by section 427B.20, but all existing credits shall continue until their expiration.
89 Acts, ch 131, §32