Final answer:
The Harpers can appeal to the boards of zoning appeals and it is advisable to seek legal assistance. Downzoning based on discriminatory practices or without reasonable cause can be legally challenged. The constitution protects against property devaluation without just compensation.
Step-by-step explanation:
If the Harpers believe the downzoning in area C has harmed their property values in area B, they have several options. They can challenge the zoning regulations by appealing to the boards of zoning appeals. These boards are quasi-judicial bodies that conduct hearings, where the Harpers can present sworn testimony. If they choose this route, it is highly recommended to seek legal assistance due to the specialized nature of zoning law.
Additionally, if there is evidence that the downzoning was enacted based on discriminatory practices, this could be subject to legal challenge. Zoning ordinances must be reasonable and not discriminatory. Spot zoning, or different zoning applied to individual parcels primarily for the private owner's interest without a reasonable basis, can also be challenged.
The Harpers also have the protection of the constitutional prohibition against taking private property for public use without just compensation, which could be relevant if the downzoning effectively diminishes their property's value substantially without serving a public interest.