I have read this in the dative (tribusviris), upon which occasion the translation given was "to the magistrates", but I am not quite ecstatic about that, with a "magistrate" (magistratus) being more of a civic official than the leader of a tribe (one of the three original Roman Tribes?) in ancient Rome. Is there a better translation...I am thinking maybe, "(to the) chieftains", or "(to the) tribal leaders" (or even "to the warlords"), as the etymology (tribus + vir) would seem to suggest?