Why are Koi illegal

koi grow up to three feet long. people who think they are pretty and who don't do any kind of research buy them for fishtanks or small ponds, and then when the fish get too big some of them are simply released into native streams, lakes, and rivers, destroying local wildlife.
 
now I wouldn't consider them wildlife destroyers, but they do compete with native bottom dwellers, like catfish and suckers, or in your case gobies, for food.
 
I remember reading a news article a few months ago how the EPA (or some similar organization) raided a chinese food restaurant because they had koi, and confiscated all of them (Maine). The owner had them for years before the ban and was really upset about it. I can understand that they can be an invasive species, but this is rediculous! They just need to fine the **** out of anybody they catch releasing them into the wild.
 
AquariaCentral.com