Re: “property of the body”:
In Canada you are not allowed to be paid for blood donations–it must be voluntary.
Presumably this is to prevent people from disadvantaging themselves by selling their organs and blood. (“Credit card debt a little high? No problem! Just sell us that kidney and you’ll be okay…” or “I just gotta sell that litre of blood to pay the rent. I know I’m blacking out at work, but it’s all I’ve got unil payday…”)
I could see where people would be pressured, by poverty of other circumstances, to sell as many body parts as they could. And it makes sense in a theoretical laissez-faire sort of way to allow this.
But once people are used to thinking of the human body as a merchandise which can then be bought and sold, ‘organlegging’ à la Larry Niven may become a lot more likely: people kidnapping people off the street for parts. Wasn’t there a recent case of a doctor taking spare parts from babies?
I suspect the whole intent of these laws is to remove the human body from the realm of commerce.