Per this case, they can not order them to sell the land at a reduced price. Here's the easy breakdown of it. I'll spare you the long case right now. Essentially a court will have to determine damages.
http://en.wikipedia.org/wiki/Spur_Industries_v._Del_E._Webb_Development_Co.
<span style="font-style: italic">Citing the "coming to a nuisance" doctrine, which prohibits equitable relief for a homeowner who purchases a home within the reach of the nuisance, the court said that Webb must indemnify Spur for his losses as a result of a move or shutdown of his enterprise. The court reasoned that, whereas the "coming to a nuisance" doctrine usually bars relief, there was a public interest at play here, and Webb's choice to come to the nuisance could not preclude the public from being protected from the nuisance. Thus, the case was remanded for determination what the damages should be.</span>