The responses to the OP are quite interesting. For the "better to ask forgiveness than permission" team, I find it sad that our culture has bred many who willingly pay no attention/respect for the laws. If you go forward in breaking the law you "might" not get penalized but you will have to stop. This could indeed cause a lot of trouble for the person staying in the trailer. Also, you can't "live" in the trailer unless you hook up to a sewer line. If you follow your local building codes you will find out soon enough if this will be allowed where you live. Of course, if you are not willing to follow the codes for the sewer hook up then you can simply do what you want to do. Forget the laws and codes.
Secondly, I couldn't find any information on line, so what am I to do?
How about going down to your city hall and asking questions like we used to do just after arriving here in covered wagons? You could call and get the info but granted, the whole process of waiting to be connected is a bit trying.
I do think you can get the information you want by talking to someone. I doubt that you would have to produce information about your exact location if you want to keep "under the radar" as someone has suggested. Just because you don't agree with a regulation, it does not give you the right to ignore it. There are HOAs in my area that have a lot of rules, most of which I don't agree with. My choice is to live elsewhere. I prefer to live in the city limits and do have to put up with some regulations that I think are silly. It is a choice that I have made. I always try to be a good neighbor and to do the right thing, even if I don't always agree.