I'm trying to translate this sentence, but I'm not sure how. It looks like either veto is the dative (substantive?) meaning 'old', or it's the verb veto, 'I stop from happening'. With 'non licet', I was thinking it made some sense to say, "whatever I may not stop from happening, it is certainly not proper", but that isn't a very coherent sentence. Another thought I had was "whatever old thing is not allowed, is certainly not proper." But again, I can't get a real sense for what this means, I'm sure there's an idiomatic way to phrase it.
[Context: The sentence comes from Cassel's dictionary, entry for oportet, attributed to Cicero]