There are two ways to look at those questions. First, AFAIK, common law holds that the dead have no property. This would limit the ability of anyone to specify that their body either could or couldn't be used for organ donation. Society, or the government, then decides what can and cannot be done, and how much notice the wishes of the departed and their family are taken into account. Again, as far as I know, it is the case that organ donation can only occur when the deceased had specifically opted to allow it, with the option of the family to allow donation if the deceased had not indicated either way. I'm sure the rules differ between jurisdictions. The common law approach would not stop a government from prohibiting cremation or organ donation if it decided to for whatever reason.

The other option would be that a person continues to own their body completely and has an absolute right to decide what happens to it. They would then be free to allow organ donation, on whatever terms they decided. I would find this view more problematic, as I don't think that the deceased having absolute rights works either practically and logically.

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T W Hopper
Member, Presbyterian Reformed Church
Currently between churches since PRC closed here - attending Crossroads Christian Church.
Canberra, Australia.