adrianus wrote:How something is used is more important than what it is called, sure, but if you don't know what it is called in a grammar you can't look up how it is used. Maybe Dative of Deprivation is nicer, but Dative of Separation was typical in older American grammars (such as Gildersleeve-Lodge, d'Ooge, A&G), and you won't find either term in the classical grammarians.
But to expand on my comment, it seems to me that you could have equally translated the passage as "for who would allow something of his to be taken by an enemy" (at least the equivalent Mod. Greek construction has this translational ambiguity), so is it really a "dative of possession"? The thing for me is that
deciding between these two options is not a question about the Latin, or in other words I don't think that "sibi" means
"from him" or "of his", even though these are suitable renderings of it. That's why I find the classification somewhat misleading.
Thanks for the reference in your other post. Some of those seem to me have alternate explanations ("ab" can already mean "on the side of") but it's still interesting. The "different to" is a good example as I don't know what the usual explanation for it is, and I can't think of anything beyond analogy with constructions of the opposite meaning.