Go to the library and ask to see the BOCA code book. In there there is the national codes for swimming pool and hot tubs. Sometimes, a township might consider a tub a small swimming pool (the BOCA codes define what is considered a swimming pool), I almost had that with my Land Use department. but luckily the head of the department was there and said "it's a hot tub". I'm still waiting for the township to approve the plans for the deck and hot tub.
Also, when you apply for the permit, some townships will give you copy of the requirements their looking for. Unfortunately pools and hot tubs do fall under the building codes. I did call the head inspector of my township before applying because EVERY electrician told me something different on what I needed to pass code, maybe you can do the same to get it clear on what you need.
Possibly, all that is needed is as Bill said - a locking cover and also a disconnect is needed to stop the spa in an emergency.
Good Luck!