Question: A non-Jewish work colleague asked me if I could buy a mezuza for her as she believes it is a good luck charm. I explained to her that we are not supposed to. Can I give her one that is passul instead?
Answer: The Gemara Yerushalmi (Peah 1:1) teaches that R’ Yehuda Hanasi gave Artaban a mezuza in return for a precious stone. Nonetheless, the poskim write that this does not mean that we can just give mezuzos away to anyone.
The Rema (Darkei Moshe YD 291:2) relates that a particular ruler once promised to act favourably towards his Jewish subjects providing that they gave him a mezuza. If they did not, he promised there would be reprisals. The Maharil ruled that they must not send it. R’ Yaakov Emden (She’elas Yaavetz 2:121) challenges the Maharil from this Gemara Yerushalmi, writing that one may certainly give a mezuza to a non-Jewish person who has promised to protect it.
However, the Rema (ibid; YD 291:2) writes that one should avoid giving a mezuza to a non-Jewish person unless it will potentially cause animosity (eivah). R’ Yissachar Ber Eilenberg (Beer Sheva 36) agrees with the Rema and suggests, among other reasons, that R’ Yehuda Hanasi gave Artaban a mezuza as it is only prohibited to give a mezuza to an idolater. Nonetheless, the Ben Ish Chai (Rav Pealim YD 4:25) notes that the Beer Sheva only suggests this as a possibility, though is not lenient in this regard. R’ Mordechai Yaakov Breisch (Chelkas Yakov YD:158) quotes the Pnei Moshe who suggests that Artevan may have been Jewish himself.
R’ Moshe Feinstein (Igros Moshe YD 1:184) writes that even when we are assured that the non-Jewish person will safeguard the mezuza, we are concerned what may happen if they pass away, and their heirs choose to discard it. He adds that it is not right to give them a passul mezuza, as that is a prohibition of geneivas daas, misleading others (See ibid. YD 2:141:3).
In conclusion, one should not give a mezuza to a non-Jewish person under normal circumstances, whether it is kosher or not.