Like I said earlier, this looks like a cold way of approaching the situation, but this is why justice is depicted as wearing a blindfold. There is way too much emotion to go any other route. With no good answer, one can only choose the lawful one.
So what's the Federation law and how do the facts--as set down in the episode--pan out?
Except you quoted no law, only what happened and the only difference between your version and mine is that I say the body belongs to Tuvok and Neelix and you say it belongs to Tuvix. There is going to be a loss of self no matter which way you turn. Every argument you make in favor of Tuvix can just as easily be made against. Tuvix was not deconstructed back into Tuvok and Neelix because he was odd or creepy, he was deconstructed because their claim to life was judged to be the greater claim.
Now it's true we don't know Federation Law, but the assumption is unless noted
because we can only perceive with modern sensibilities, the law must be comparable with ours. It is the producer and writer's job to tell us if something is different. The question is and has always been "who owns my body." We are fighting a great political war right now in the US over this very question.
It's a fight that questions another's right to tell us who we can love, and how to express that love. They want to tell us what we can do with our own bodies. Out of this will come laws, one way or another. But I am choosing to fight for the right to my own body and how it is used.
You should have every right to say "I wouldn't want my life back in such a situation," but you have no right (nor did Tuvix) to make that decision for anyone else. It would have been totally immoral and unethical to not take Tuvok's or Neelix's feelings into consideration. Yes this was the result of an accident, but they also didn't have a choice and when you get down to the bottom of the argument, I think that Tuvok and Neelix had the better argument, especially in light of what is going on now.
Now in my opinion and again IMHO, I believe the laws governing organ donations will be even more stringent in the future. And that opinion is based in the knowledge that even as we speak there is a black market for transplant organs. How much better do we have to get at repairing bodies with donor parts for this to become a world wide problem involving the murder of people and the harvesting of organs?
(An aside here... The only way current transplant law fits as a precedent for this case is in the cases of live donors. We cannot force a living donor to give up a portion of his or her body to save another--not even an identical twin--if the donor forbids it. No one can force you to risk your life to save another).
You are not quite right, the law in the US and Canada expressly forbid the use of anyone's body even after death unless permission has been given either by the person who gave permission before his death, or the permission of the next of kin afterward.
I actually find it funny that we in the scifi community discuss these ethical issues to death, and when they come into the mainstream they don't even create more than a "huh".
I'm specifically thinking of some news stories on cloning, a few years ago, that generated no angst as far as the network news anchors were concerned. I recall one of them suggesting, when a cloning story was introduced, that "nothing will ever be the same again" and my heckle from the peanut gallery was... "sure it will... it will be the same over and over until the copies degrade beyond use."
Well... I'm being extreme.. I do remember back in the 90's how a family got some guff from the public by having another baby to save the life of their teenaged daughter who needed a transplant.
Well I'd like to believe we think deeper than a lot of people LOL. But I think there has been a lot of Science Fiction that deals with these dilemmas. We all know that Trek was especially good at this. The best Science Fiction I can think of that deals with organ donation and "organleggers" is by Larry Niven. He has three really good short stories and a couple of novella's put together in one book that is still available on Amazon. Flatlander