Human-Vampire Contracts

Human-Vampire Contracts?
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2332596
In your opinion, should it be legal or illegal to buy and sell blood? Professor Guerra-Pujol, for example, has taken the position that agreements between
humans and vampires for the purchase and sale of blood should be 100% legal. (See here
Links to an external site..) Do you agree? Why or why not? (250 words)