This is an easy one. Hold my beer:

-This country was founded on private property rights. What is being described in the article amounts to a taking of some of those rights from the current property holders. Courts of law do not truck with such takings.

-Assuming those who received the letter and may be affected are fee holders (i.e., they own their land and the improvements thereupon) and that their current use of that land and improvements constitutes a legal, conforming use thereof, a change in zoning like that described then usually makes the land in question and its use a "Legal, non-conforming use". That means the owner (or a lessee of that land and/or improvements) can continue to use the property under the zoning guidelines in place at the time the property was first put into use. (For example, if the land is zoned for retail use and the owner has a retail pharmacy on the site, that is a legal, conforming use so long as the building conforms to the zoning requirements in place at the time the improvements were constructed. If the zoning is later changed to, say, residential, that pharmacy may continue to operate as such, until such time as the improvements are demolished, after which time the land must be then used in a manner consistent with current zoning regulations.)

-The concept of a legal, non-conforming use after a zoning change is widely understood in this country and courts of law see any restriction based on change of zoning (e.g., telling our pharmacy owner he must now use his property for residential) as a taking of property rights, and such cases are almost always won by the property holder.

-All those on the Right complaining about 'too much regulation' quickly become fans of concepts like zoning and legal non-conforming use of land when someone shows up and gets in their face and tries to take the ownership rights of their land...

Eminent Domain actions require that the state, upon taking, provides 'just compensation', which usually leads to two appraisers battling it out over their valuations of the taken property. The person losing their property has the right to appeal in court, so these matters can drag out a long time with no transfer of the property until the matter is concluded. Most of those doing the taking cannot wait around that long, so usually settle in a relatively fair manner.

As for the courts ignoring property law, remember this is going on in Texas, where property law is maybe a bigger deal than just about anywhere else, because of oil, grazing rights, and also because it's Texas...