> Note that Accept-Language is a list of languages, not a single one
Ah, that's a good point, I wasn't aware of that. My feeling is that JAX-RS should select the right Locale (however that would look like), so it can apply it across all sorts of providers/services it interacts with and then pass that one to Bean Validation.
> one of the main motivations for doing this is to provide support for MVC
I'm not so sure about that, I think JAX-RS itself would benefit from it, too.