For the most part electrical codes are standard throughout the U.S., but local areas have their own modifications to the National Electrical Code. I don't know why this is, but maybe because some areas are quite cold, others quite hot, some dry, some very wet, some have earthquakes, etc. Maybe regional differences cause certain problems to crop up and they modify the code for this?
For example I've seen modifications in some areas for flex conduit installation.
Anyway conduit is a good thing because it protects the wiring. Also even if it was not required, I would run the new wiring the same just for "looks".
If you are interested in the code for this, go to your local electrical inspector's office and just ask. The offices in my area have certain times of the day where anyone can go and ask questions. Take plenty of pictures of the area where you want to do the work. Then the inspector can better determine what would be required.
It is no big deal to get a permit in many areas. Plus then you have an expert checking your work to be sure it is ok. A good learning experience!