Non-Jews are prohibited from eating Eiver Min HaChai (a limb from a living animal). This law is derived from G-d’s directive to Noach: “But flesh – with its soul, its blood you should not eat” (Bereishit 9:4). Later, at Matan Torah (the giving of the Torah on Mount Sinai), Jews too were forbidden to eat Eiver Min HaChai. This prohibition is derived from the sentence: “You shall not eat the life with the meat” (Devarim 12:23). If this prohibition had not been repeated, it would not have applied to the Jewish people, since we do not derive laws for Jews from stories that preceded the giving of the Torah.
The basis of the prohibition is different for non-Jews and Jews. A non-Jew is not permitted to eat from an animal while it is still alive, while a Jew may eat from an animal only if it was slaughtered in accordance with halacha (shechitah). Thus if an animal was slaughtered properly by a Jew but is still twitching (mefarches) afterwards, a Jew may eat the meat since shechitah was performed properly. However, since shechitah is not relevant to a non-Jew, if he eats this meat he is transgressing the prohibition of Eiver Min HaChai.
