What will the Kohanim rule about?
Malbim: They will rule about laws of Kodshim, Tum'ah and Taharah. Laws of Kodshim are handed over only to Kohanim who engage in them 1 ? therefore it says "Es Ami Yoru." The laws of Tum'ah and Taharah, also Bnei Yisrael know them, like in the days of Chizkiyah, everyone was expert in them, just [Kohanim] will inform them if some Tum'ah touched. Therefore, it says "Yodi'um". Chazal said, "Da'as" (Yeshayah 33:6) hints to Seder Taharos (Shabbos 31a).
Also Yisrael engage in Kodshim ? they eat Korban Pesach, Shelamim?! And even if the laws affected only Kohanim, the entire Torah was given to all of Yisrael to learn and rule about it! This requires investigation. (PF)
