Stephen Skousen has pointed out (personal communication, 14 July 2006) that the usage seems contradictory in this verse when compared with the earlier text (in the preceding verse as well as earlier in Ether 3):
Notice, however, that in all three of these cases we have the preposition from, but here in Ether 12:21 there is no from (“for he could no longer be kept without the veil”). This difference suggests that from requires within. We appear to have a change in perspective: the phraseology “keep from within” is from an external point of view (such as from the brother of Jared’s perspective) while “keep without” is from an internal point of view (from the Lord’s perspective). Notice also that in Ether 3:19 we have the verb behold (“he could not be kept from beholding within the veil”), which is definitely from the brother of Jared’s perspective. In any event, there appears to be a systematic difference here in Ether 12:21, and this difference is probably not an error. The critical text will therefore maintain the unique reading in Ether 12:21, “for he could no longer be kept without the veil”.
Summary: Retain in Ether 12:21 the original phraseology, “for he could no longer be kept without the veil”; although this phraseology is unique, it appears to represent the situation from the Lord’s point of view.