On the first day of Sukkos you need to own a lulav to be yotzei ("lachem"). You can't borrow a lulav, but you can accept someone else's as a matanah, a gift. The giver has a right to stipulate that the lulav must be returned, a matanah al menas l'hachzir. The Rosh writes that to satisfy this condition the borrower must be makneh the lulav back to the original owner with a formal kinyan (which is why this would not work with a child, who has no right to be makneh things). As we once discussed, the Ketzos (241) disagrees and says a matanah al menas l'hachzir works so long as the object is returned, even without a formal kinyan. According to the Ketzos, matanah al menas l'hachzir is a "kinyan l'zman", a form of temporary ownership in effect for a specific duration of time., e.g. so long as it takes to perform the mitzvah of netilas lulav Once the time is up, the original owner automatically resumes control without a formal kinyan being required. At the heart of the dispute is the following question: is temporary ownership sufficient to satisfy the requirement of “lachem”?
Last post we discussed the case of stolen schach that m’derabbanan is considered part of the sukkah for the duration of sukkos (i.e. the thief has no obligation to dismantle the sukkah and return the stolen goods), but after sukkos, once the sukkah is dismantled anyway, must be returned. The Avnei Miluim (28:53) offers this case as proof that he is right -- ownership of the schach even for the limited duration of a week is considered sufficient to fulfill the mitzvah of sukkah even according to those Tana’im who require "lachem" md’oraysa for sukkah.
Is this proof really ironclad? My son suggested that one can distinguish between these cases. In the case of matanah al menas l’hachzir of lulav, it is the choice by the owner to grant temporary ownership instead of full ownership which is seen by the Rosh as limiting the kinyan, diminishing “lachem”. In the case of the stolen goods, the kinyan lasts only for a week not because of any choice by the owner or recipient, but simply because the chachamim re-imposed the obligation to return the goods after the sukkah was dismantled. (R’ Scheinberg draws a similar distinction in Mishmeres Chaim vol. II.)