I would love to see the amendment requiring that.
I would love to see it too. I can only go by what I have learned by getting turned down for something the inspector says is a local requirement. I have tried to acquire some type of documentation listing all the local codes. Sadly either there is none or I have yet to find the right person to ask. I have some documentation from the mid 80's and we do sometimes get amendments sent to use but a lot of the times we find out what they are when we get turned down for something.
One example which is not very good.
An 8' ground rod is suppose to be 8' in the ground. (Don't have my code book handy so I do not know the correct wording)
In Bartlett, Arlington and Collierville which are in Shelby county, but have their own inspection offices, the ground rod must be 8' in the ground and have a clamp listed for direct burial.
In all other areas of Shelby county, the ground rod must be exposed above the ground with the clamp accessible.