Yes. It is indeed legal if both parties give their consent. Although it is considered taboo, there is no law stating you cannot consume the flesh of another living being. Usually, the guy caught eating the corpse is charged with murder. But if the guy is alive, kicking, and has given you explicit permission to hunk off a piece of his flesh, it's legal. It's also legal to own a flamethrower and drive a tank in the street so long as the cannon is disabled and the treads are switched from steel to rubber.