The gemara[1] states that the renter of a house has the obligation to affix mezuzot, but he may not remove them when he leaves. The early authorities offer two basic explanations: Tosafot[2] say that it is out of concern that leaving the house without mezuzot will endanger future inhabitants. The She’iltot[3] assumes that the reason is that removing mezuzot from use disgraces them. One practical difference between the approaches is whether one may remove mezuzot in order to affix them promptly elsewhere.[4] We usually follow Tosafot, but if it will be difficult to find other mezuzot for his new apartment, one may rely on the She’iltot and transfer them.[5]
If one must leave the mezuzot, he can demand the value of basic kosher mezuzot from the owner of the apartment.[6] If one has a special mezuza that he wishes to bring to his new home, he can replace it with a simple one that he will leave (and be reimbursed for) and put up the special one in his new home.[7] One may certainly switch or remove the mezuza cases.[8]
The above applies only if one was renting from a Jew. If he rents from a non-Jew, then he should remove the mezuzot[9] to protect them from potential disgrace.[10] Similarly, if the owner is a Jew who would take off the mezuzot and not know how to respect them, one should remove them. In addition, if a Jew owns the apartment but the next tenant will not be Jewish, there is no reason to leave them.[11] If a non-Jew owns the home, then one does not have to leave the mezuzot even if the next tenants are expected to be Jews.[12] Finally, even if everyone is Jewish, the new occupant has the right to change the mezuzot. Such a switch can be coordinated between the outgoing and incoming occupants in a manner that will allow only a short time to pass before the latter tenant affixes mezuzot to his home.[13]