I'm an Italian Noahide.
My question may seem abstruse; I try to explain myself better.
The Noahide Law is notoriously codified in seven macro-obligations, in turn specified in more detailed precepts; however, the Halakhah includes further prohibitions concerning the Gentiles, prohibitions that are not specifically included in the Noachide Law.
I quote for example:
-The observance of the Shabbat is forbidden to a Gentile (see Talmud Bavli Sanhredrin 58b)
-The marriage between a Jew and a Gentile is forbidden, as is any sexual intercourse between them (see Mishneh Torah-Issurei Biah 12:1)
But then, on the basis of the principle "nullum crimen, nulla poena sine lege", why should the Noahide Law also not encompass precepts such as those mentioned above?
If a particular halakhah prohibits the Gentiles from having a specific conduct, I believe that it is binding on the Gentiles themselves, and that therefore they should be informed of the existence of such rules, so that the Gentiles are put in a position not to infringe this type of prescription.