Hopefully they are in Agricultural Zoning. If so, the local zoning board will have to stuff it. The Right to Farm Act should supercede any local ordinances. Another aspect I'd have my legal team investigate is the articles of incorporation for the municipality. If they've improperly incorporated they will be an illegal entity and illegal entities who collect taxes are down-right frowned upon. I bring this up because I know of another municipality, in Oakland county, who went through something like this. The woman they chose to bully had sharp teeth and uncovered this dirty little secret. Rather than expose it, they gave her a "varience." But the ground-work is there anyone else to take a hammer to the glass.
Just an update on this case: They won the court case and can continue farming! The judge ruled the farm is in compliance with the GAAMPS and is therefore protected by the Michigan Right to Farm Act. Props to the Farm to Consumer Legal Defense Fund for representing the Buchlers. Huge victory for all Michigan small farmers.