"As to your question about the nations, know that the Lord desires the heart, and that the intention of the heart is the measure of all things. That is why our sages say 'The pious men among the Gentiles have a share in the World-to-Come,' namely, if they have acquired what can be acquired of the knowledge of God, and if they ennoble their souls with worthy qualities. There is no doubt that every man who ennobles his soul with excellent morals and wisdom based on the faith in God, certainly belongs to the men of the World-to-Come. That is why our sages said, 'Even a non-Jew who studied the Torah of our master Moses resembles the High Priest," Rambam, Letter to Hasdai Halevi, 12th Century, as quoted in Jacob S. Minkin's "The Teachings of Maimonides"
"R. Johanan said: A heathen who studies the Torah deserves death, for it is written, Moses commandedus a law for an inheritance; it is our inheritance, not theirs. Then why is this not included in the Noachian laws? — On the reading morasha [an inheritance] he steals it; on the reading me'orasah[betrothed], he is guilty as one who violates a betrothed maiden, who is stoned. An objection is raised: R. Meir used to say. Whence do we know that even a heathen who studies the Torah is as a High Priest? From the verse, [Ye shall therefore keep my statutes, and my judgments:] which, if man do, he shall live in them. Priests, Levites, and Israelites are not mentioned, but men: hence thou mayest learn that even a heathen who studies the Torah is as a High Priest! — That refers to their own seven laws," B.T., Sanhedrin, Folio 59a, taken from halakhah.com.But it turns out that there is a much earlier version of this in Sifra. Sifra was a midrashic commentary on Leviticus that came out in the Second Temple era or perhaps circa the Bar Kochba revolt (see note at end of post). Notice that the earlier Sifra version does not have anything in it about the so-called "Noahide Laws":
"From where do you know that a gentile who practices the Torah is equal to the High Priest? There is a teaching in this respect in the Scriptural verse that reads, '[You shall observe my decrees and my laws,] which man shall carry out and by which he shall live' (Lev 18:5). And likewise it says: 'This is the Torah of man, O Lord God' (2 Sam 7:19). It does not say: 'This is the Torah of Priests, Levites, Israelites', but, 'This is the Torah of man,'" (Sifra, Ahare Mot 13:13, I. H. Weiss edition)It's just purely One-Law. I then realized that Rambam wasn't quoting from B.T. Sanhedrin 59a at all. I only assumed that he was because I was unaware of the Sifra passage. (However, Rambam elsewhere specifically references B.T. Sanhedrin 59a and incorporates it into his halachic decision-making).
The most frustrating thing about B.T. Sanhedrin 59a is that the underlying argument from Leviticus is that "man" (mankind broadly, not any particular ethnicity) is supposed to keep the chukim and mishpatim (i.e. the Torah of Moses, which is exactly what Rambam references in his letter) yet---YET--the Talmudic rabbis completely set this aside and replace it with the so-called "Noahide Laws."
Now, in defense of the rabbis, maybe they were reacting to Christian persecution at the time--I have no idea. But this little interpolation of Noahide Laws cannot be sustained in light of Jewish Tradition (from Sifra, and from the wording in Leviticus).
...unless someone has a different opinion. I'm open to anything I may have missed.
"An early version of Sifra even dates back to Hasmonean times. Stemberger, however, can prove that Finkelstein's arguments do not bear close examination. The preferred exegetical rules of Ribbui (amplification) und Miut (restriction) rather show that the text in its oldest version can hardly have been written before 70 and in any case has to be dated to rabbinic times, to the decades after the Bar Kochba revolt at the earliest," Rendtorff, et al, "The Book of Leviticus: Composition and Reception, Volume 93", pg. 407