Actually, it doesn't.
Talmud Sanhedrin 59a
Rabbi Yochanan said: A gentile who studies Torah is liable for death as it says (Deuteronomy 33:4) "Moses commanded us Torah as a heritage." It is a heritage for us and not for them... Rabbi Meir would say: How do we know that even a gentile who engages in the study of Torah is like a Jewish high priest? As it says (Leviticus 18:5) "Which man shall do [i.e. study] and by which he shall live [in the afterlife]." It does not say "priests, Levites, and Israelites" but "man". We learn from here that even a gentile who engages in the study of Torah is like a Jewish high priest. [We answer the contradiction between Rabbi Yochanan's statement and Rabbi Meir's that] there [Rabbi Meir] is referring to their seven commandments.
The Talmud provides a contradiction between two statements regarding whether a gentile is allowed to study Torah. The accusation only quotes one side and does not provide the resolution. By seeing the whole text and the resolution we can better understand the Talmud's intent.
What the accusation also does not quote is the passage immediately preceding ours. The Talmud states that it is forbidden for a gentile to fully observe the Jewish Sabbath and holidays. While this does not seem as conspiratorial as the prohibition against studying Torah it is still curious. Why should it be? The explanation is tied to the Talmud's resolution to the contradiction between Rabbi Yochanan and Rabbi Meir. The Talmud concludes that both rabbis agree but one was stating that a gentile is forbidden to study the parts of Torah that discuss the commandments relating specifically to Jews and the other was stating that a gentile is highly praised for studying the parts of Torah that discuss the commandments that relate to him. In other words, a gentile should be concerned with his role in G-d's world. He should actively pursue his place in the divine plan and attempt to raise himself to the highest human levels. However, as a righteous gentile, he must confine himself to HIS role and not someone else's role. When he starts studying about Jewish commandments and observing Jewish holidays, he is stepping out of his role as a righteous gentile and entering the role of a Jew. This is as inappropriate as if a Jew would start acting in the role of a righteous gentile. We all have our roles in the world and it is wrong to try to side-step those roles. A gentile can become a Jew through conversion but a righteous gentile is righteous in his own right and is forbidden to try to over-step his role.
Reconstructionist Jew - raised Conservative
(answer from talmud.faithweb.com