For your consideration ...
Thank you for posting that link.. Does the fence need to be around the pool area directly or if the whole yard is fenced is that fenced?
My point is, you wanted that person fined because a horse fell in.. and it might have already had the legal requirements of fencing and safety equipment (pool cover) that would have withstood people/kids from falling in.. but you want them fined.. You seem to want the expectations of safety for a horse.. so why not all animals.. why should horses get specially safety treatment over other animals.
Looking at the pictures, there is no obvious fencing anywhere on the property. I didn't want them cited because of the horse falling in, I wanted them cited because of the danger and liability with an in ground pool not properly fenced. Though had there been a fence, the horse wouldn't have fallen in the pool to begin with. Pool covers are not made to keep people or animals from falling in pools, they are covers to keep the elements out such as leaves and other debris. Not sure of the requirement to perimeter fence immediately around a pool, or if a total backyard fence is enough.
I know you have a hair up your ass about certain aspects of our current society, (stupid laws, rules, regulations, edicts, policies, statues, etc., that encroach on our personal liberties), I do as well. But there have been many a sad day when a child has wandered away from supervision and drowned because of pools lacking a perimeter fence. It's just logical, and an element of added safety, to fence an in ground pool, if not for an owner's piece of mind, then to stop any possible accidental deaths.