A few years ago, my wife and I actually fought the county over something that was not written into ordinance regarding pet rabbits. We had pet rabbits that our children showed. A neighbor told the county that we were running a breeding and production operation so the county said we were breaking the law (county zoning ordinance; no written statement regarding rabbits) and we had to get rid of them. We spent $4000 fighting it with attorneys and what I learned out of this is:
1. There is no written civil law regarding animals. These are ordinances written by your city, county, state.... Ordinances are not civil laws. Ordinances are written by a group of appointed or elected officials who determine what is considered legal and illegal regarding the use of property. They have to make the meetings public, but do not have to listen to the public. They can write the ordinances the way they want and can be interpreted the way they want. There was no written ordinance regarding rabbits specifically.
2. We brought in experts from around the country from the American Rabbit Breeders and the USDA regarding what it was considered to be a producer and if rabbits were considered livestock. (by the way, no where else in the county are rabbits considered livestock except for our old county). We still lost.
3. Moral to the story: Don't spend a lot of time fighting over ordinances. They are just pieces of paper that a group of people in a room determined to be what they envisioned for their county, city, or state.
4. Since our public case, I have read about 4-6 backyard chicken owners who had to remove chickens because the same group of old men sitting at a table deemed them to be livestock producers. (producing eggs is still livestock to them).
Good luck with getting to keep them and building the tractor. Don't spend too much money as they still may come back to bite you in the end.