They knew about the restrictions when they brought the property and if the property was unsuitable for their needs, thne they should (a) brought another property someplace else that did nothave the restrictions: (b) work to legally change the law; or (c) comply with the code to obtain the required permit before installing the pool in violation of the code.
From reading your posts, I have the impression that you are against any property use restrictions of any kind even if one person's use of their property impair's the use of value of neighboring properties. Many suburban municipalities, for example, have a code provision that prohibits a landowner form installing a pool or deck within a certain distance of a common boundry with another residential property. The obvious reason is so that one neighbors' use of their pool and deck does not disturb another neighbor's good night sleep. Based upon your comments, however, I'm sure you wouldn't mind if your neighbor put a 24' above ground pool and deck with bright lights for all night parties, a 12 speaker sound system, kegalator, and a smokey fire pit six inches from the boundry line, right under your bedroom window.
Absurd. That would be a real detriment to the neighbor. So would running a commercial enterprise in a residential area. As I stated before, what was the harm to the neighbors or community in this case? Half million dollar fines? For a so-called wet land? This is government run amok. That you support it says more about you than my objection does about me. I can distinguish between the reasonable and the absurd.