americana-lover, I'm certainly no expert, but have been trying to understand the Michigan Right to Farm Act (MRTFA) for about a year now.
My understanding is that if you are happy with the provisions of your city ordinance (a certain number of hens, no roosters, no sales), then you should just keep to those rules and be happy with your chickens.
However, some local ordinances in Michigan do not permit chickens, or roosters, or bees, or some other agricultural animal. People who want to keep these animals in areas that restrict them can use the state-level, MRTFA law to win protection to keep their animals. In a nutshell, the MRTFA protects your right to keep farm animals in Michigan without regard to local ordinances or zoning laws if you meet three requirements:
1. Establish a farm operation (keep chickens)
2. Develop a commercial aspect to your farm (sell eggs, chicks, feathers, compost, etc. to friends, neighbors, farm market etc.)
3. Follow good management practices (the rules are called GAAMPS, but are just reasonable attempts to keep a clean operation)
I really encourage you to check out the MRTFA thread if you're at all interested.