A common trope in science fiction is that in the future meat is grown as a tissue culture in vats rather than as part of a living animal. This is obviously more humane as nothing with a brain has to be slaughtered.
This is now moving out of science fiction, with some laboratory demonstrations of vat-grown meat. At present this is very expensive, but the hope is that industrialisation will bring the price down to something comparable to in-vivo meat.
From this its an obvious small hop to the idea of growing human meat by starting with a small biopsy from a willing volunteer. Two works which include this are the short story The Food of the Gods by Arthur C. Clarke (in which a meat manufacturer reveals the dark secret of his competitor's hit product) and a passing reference to the "Morningside Cannibals" in Rule 34 by Charles Stross (in which the police had busted a group of friends who dined on cultured meat grown from each other, but then couldn't figure out what to charge them with).
So the question is: would it be legal to eat cultured human meat produced in this way? And if so, would it be legal to sell it?
I'm not including a jusridiction here, so feel free to describe the law anywhere.