Another way of dealing with this is to have a "the bid amount shown includes only the work listed - additional work (outside the scope of this bid) to meet code compliance required by the inspector/AHJ will be performed on a T&M basis" clause in your bid and/or contract.
North Chicago had a similar attempt a few years ago - as part of their occupancy inspections, they would require compliance with the '96 NEC, and the NCEC - little things like no exposed BX in basements longer than 2', hardwired smokes, GFCI's in kitchens and baths.
It was a great time to be an EC in North Chicago - unfortunately I was a pirate at the time, and couldn't pull permits for that kind of work
Somebody finally challenged that behavior, under the argument that if it was compliant with the NEC/NCEC at the time it was built, as long as there were no IDLH threats, the City couldn't force compliance to a newer Code. Don't know if it ever actually made it to court or not, but that type of service call has really diminished in town.