Is a non Jew allowed to wear the tablets of the 10 commandments as a necklace?
I am sking this question because I heard that a non Jew is not allowed to wear a mezuza as a necklace even if it is not a real mezuza.
I viewed this wiki article which presents various viewpoints on not just the mezuzah issue but the concept of Noahides performing Jewish mitzvoth. While there are various viewpoints, there is a common denominator regarding the mezuzah.
The prohibition is that Noahides are forbidden from affixing a kosher (real) mezuzah to their doorposts. There is nothing stated about wearing a kosher mezuzah as a necklace, though, I could see some problems for even a Jew doing this, as it has G-d's name in it and could be treated improperly or disrespectfully. Thus, a similar problem would occur if the 10 commandments charm uses the 4-letter name of G-d (or any Hebrew written name of G-d) on it, as even Noahides are commanded not to desecrate G-d's name.
Beyond that, if it is neither a real mezuzah or the symbol of the 10 Commandment tablets with, say, no "inscription" or not having G-d's name, I can't see that as problematic.
As far as possible concerns of mar'it ayin (loosely translated as other people who see this will assume your violating a prohibition), I think these days, the majority of the public is accustomed to people wearing various charms as a necklace. Certainly, regarding the 10 commandments, no one will think that they are the "real" thing, anyway, b/c a real Torah wouldn't fit around your neck!
To verify all this, speak to a competent rabbi.