In speaking with different clubs versus the association leaderships I've found over the years the rules vary. There are some common threads though and the point made in the other thread I've seen occur also at the Central Florida Show where (the same leadership as this show) strictly applies their interpretation of what they believe the appropriate ZNA standard to be. Bateman recently described this years show in the Netherlands that he particapated in judging and both vendors and hobbyists compete and everyone was generally happy with the arrangement.
I chuckle along with some breeders at this rule that typically becomes an issue when someone buys a fish from a breeder or dealer at the show prior or during benching and then wants to enter the koi in competition.
Those in the business that I've spoken to have made a valid point as few fish actually in competition actually were raised from spawns in the owners pond. Taking these rules to extreme might require some sort of bill-of-sale prior to showing a fish to determine how long the owner had possession of the fish prior to show. Is the standard six months or two years required for ownership? I believe the rule is more related to not being able to purchase the fish from a vendor booth, but if you bought it out front before bringing it in that would be fine. I'd like to see the actual rule as it is written versus interpreted.