kedushas eretz yisrael

The Rambam (Sanhedrin 4:6) quotes the halacha that smicha can be given only in Eretz Yisrael, the boundaries of which are defined by those areas captured by Yehoshua.
וכל ארץ ישראל שהחזיקו בה עולי מצריים, ראויה לסמיכה.

The Minchas Chinuch asks: the Rambam elsewhere (Hil Terumos 1:5) writes that the kedusha of Eretz Yisrael established by Yehoshua’s conquest was negated by the first exile; Eretz Yisrael was resanctified by Ezra when the nation returned from Bavel, and only areas sanctified by this second enduring kedusha are included in the halachic boundaries of Eretz Yisrael. Why with respect to smicha does the Rambam refer to the original boundaries, which were negated?

Rav Soloveitchik quoted an idea from his father to answer this question. In Hilchos Terumos the Rambam is discussing the sanctity of the land viz. agricultural mitzvos. In that context, the Rambam addresses himself to defining what areas of the Land were endowed with kedusha by Ezra. However, the idea of Eretz Yisrael as the land chosen by G-d and promised to the Jewish people encompasses far more area than that which Ezra reclaimed. When it comes to smicha, the Rambam invokes this far broader concept. Smicha is not dependent on the sanctity of the land, more broadly on the idea of a promised homeland in which the transmission of mesorah can function as an ideal. There are many other proofs to this idea of R' Moshe Soloveitchik - maybe more on this in later posts.