According to the Gemara (2a) Rabbi Ḥanina bar Pappa offered a homily suggesting that at the End of Days God will hold a Sefer Torah and announce that the ultimate reward will be given to those who involved themselves in Torah study. In this context the Gemara quotes the teaching of Rabbi Meir who teaches that a non-Jew who studies Torah should be treated like a kohen gadol. This is based on the passage (Vayikra 18:5) that says that we must perform the laws of the Torah that a person does – asher ya’aseh otam ha-adam – and the terminology used is the generic ha-adam – “a person” – rather than Jewish people, like kohanim, levi’im and yisra’elim. Thus the credit given to someone who studies apparently applies even to non-Jews.
Tosafot note that according to the Gemara in Sanhedrin (59a) non-Jews are prohibited from learning Torah based on the passage (Devarim 33:4) Torah tziva lanu Moshe morasha – Moses commanded the Torah to us as an inheritance. The only exception would be the study of the seven Noaḥide laws, and Tosafot suggest that this must be Rabbi Meir’s intent. The Maharsha adds that we should not view the Torah that is permissible to non-Jews as being limited to those seven mitzvot. In fact, there are many Torah laws that apply to non-Jews aside from those seven that are emphasized because of their severity.
The Meiri argues that Rabbi Meir is speaking about the entire Torah, and that the Gemara in Sanhedrin that forbids Torah study to non-Jews is limited only to those whose interest in learning Torah stems from curiosity or an academic interest in the subject. If, however, the non-Jew is searching for truth, which leads him to the Torah, or if he studies the Torah and fulfills it out of a sincere desire for a relationship with God, then this is not only permissible, but he is considered to be like the kohen gadol.