So a dead guy's body still belongs to him and it goes where he planned it would go after his death. To the university to be dissected by med students, or a grave or whatever. His kid's can't just ignore the will and dump his carcass in the river or whatever, because it's not their property either.
So I'm curious about this. Why do we allow people to refuse to donate their organs? I mean, the reasons for it amount to "it creeps me out", and after you're dead, you won't be creeped out by it. Shouldn't the needs of the living take precedence?
Overall, the way you frame a question is key and this is a major hurdle to practicing law. People come in and they tell me what they think happened in their terms. I can't use those terms, I have to use the law's terms if I want a judge or magistrate (someone who can do something about it) to give a damn.
The basis of our rights begin with bodily integrity: the right to be free of unwarranted harm from others. From there, it abstracts out with different definitions of "harm" and "unwarranted." "bodily" also becomes "property," etc. (Property rights as an idea, developed from the idea of bodily rights).
If a person has a right to determine their bodily integrity and their property disposition, then the primary thing about death is just that they can't communicate how they want their bodily integrity or property disposed of.... Enter the will, a document that communicates the person's desires. This is "the intent of the testator" or what the person wants done after they're dead. It's the main consideration in a will, but not the only one. It just isn't absolute, because there are certain things we won't let you do and screw you if you wanna do them.
The first thing we won't let you do is disinheriting your spouse or leaving them with nothing. A.) We the state don't want to take care of your spouse after you're dead if you have the means to do so. It's expensive and you gain unjustly as a result of his/her loss. B.) That stuff is their stuff too. This is why there was dower (now only in four states including Ohio by statute) and what is called an "elective spousal share." The amount of the spousal share is determined by statute. Here, this is somewhere between 1/2 and 1/3 depending on the number of children in the family.
The second thing we won't let you do is make racist/bigoted distributions of your property. You can't leave your kid "$20,000 so long as he is married before the age of 27 to a woman of pure white lineage." We disallow this as against public policy. What happens to the money after the condition is disallowed is a whole big steaming court case. However, strangely, certain conditions which might be considered bigoted might be allowed. Example, "I give to my nephew Issac the sum of $70,000 so long as and only if he should use it to purchase a home in the State of Israel and maintain his Jewish faith in accordance with the Torah while volunteering 1 hour a week to a charity serving Survivors of the Holocaust," may be allowed or disallowed depending on jurisdiction.
As you can see, we place a great value upon what the deceased wants done with both their property and their body. To override this, there usually has to be an issue of public policy forbidding their wishes.
Thus, to seriously consider your question, "Why do we allow people to refuse to donate their organs? " You would have to consider if it is a very serious matter of public policy sufficient to override their basic right to bodily and property right determination, even after death.
If you wanted to frame an argument, it could be something like this. While it has long been recognized that one has the right to determine what is done with their body and property after death, it is also long recognized that this right is not absolute. Certain public policies may override the right to determine what is done with one's body and property after death. Examples include elective spousal share to avoid disinheriting spouses and nullifying bequests and gifts in the will if made with racial or bigoted motive. Both of these long standing doctrines are justified in overriding the will of the testator because they impose undue burdens upon the public and state they are not willing to bear.
[Talk about Organ donation problems including the death statistics]
[Analogize refusing to donate organs to refusing to give widow/widower spouse support after death]
[address differences and imperfections with this analogy including how you are related to/have chosen your spouse]
[state that despite these differences the case remains strong because while you are not related to an individual dying for lack of an organ, the need is greater--life itself rather than mere financial support]
Who knows if it would work (I'd bet not) but there's a way to do it and how you do it is just as important as why.