Ox, I totally agree: ask before doing. But after 25 years in automotive and watching my wife deal with the building department for longer than that, and my own dealing with the Ag sector, I have the experience to say that a lot of the time they do not know what they are doing, and they very definitely make things up so as not to appear to be ignorant on a given issue. There are some people who are conscientious, knowledgeable, etc., but you cannot operate from that assumption. One local government office has a sign hanging in their lobby to the affect that they will look up info for you, or you can do it yourself, but if they miss something (and they do) they are in NO way responsible, even though they are the official keepers of the info and the supposed experts.
There are rules, regs, bureaus, departments, etc. that you don't even know exist, but they will have a finger in your business life, and often, when they raise their head, your business comes to a halt.
It is basically a "buyer beware" approach to all of this stuff. Certainly wish it was otherwise.