I can see both sides of the story, I do feel for this guy and his fish, after so long together I just can't get my head around someone who made a law after he bought it saying 'sorry and all but the law say I have to kill it' There has to be an alternative option, people have said move it to Canada/Uk great but that would be illegal, if the fish has been purchased after the ban then it's a different story but it wasn't. I don't know the law over there so I can't really comment on that, but I've seen many threads about illegal fish being kept in public aquariums, with difficult to obtain permits, this has got to be the way in this case.
The only thing I can relate it to over here is the dangerous animals act 1976 , a lot of exotics were released into the wild, this is simply not the case here, fish was purchased in 99 the law was changed in 04, if he was going to release it he would, it's been 5 years since.
I hope a sensible solution is found