Why does the Torah insert the words "be'Chol Moshvoseichem"?
Ramban: Beis-Din are obligated to convene at all times, even after the Churban and even in Galus, to judge Dinei Kenasos, Gezeilos va'Chavalos and other money issues and the sentencing of Chayvei Malkos. 3
See Sifsei Chachamim.
See Ramban's objection to this explanation.
Ramban (citing Sanhedrin, 52b and Mechilta): Based on the Pasuk in Devarim 17:9, they may only adjudicate with regard to the Dinim that involve Misas Beis-Din as long as the Kohanim are serving in the Beis-Hamikdash, but not after the Churban. This is because we only Darshen "Chukas Mishpat" in this Pasuk in cinnection with the Dinim of Misah - mentioned earlier in Pasuk 12 & 24 (See Ramban).