Well, there are a few health things to keep in mind when attempting to eat humans. First of all, stay away from the central nervous system (brain, nerves) as eating them can have rather bad effects on you. Second, while many internal organs can be eaten, make sure they are properly cooked, as many contain various forms of bacteria that may prove harmful to someone not originally their host.
Also, be wary of bloodborn diseases as they can easily transfer via contact with an open wound.
Now, as to practicality. So far as I know, there is no direct law outlawing cannibalisim, however there are several other laws that the act may break depending on how it plays out.
Murder and assault are obvious ones, so your food needs to be alive and willing.
This all said, you should probably leave this to the realm of fantasy, but you might meat that special someone some day.