SAX and xmlns-uris

I was looking for wording related to the xmlns-uris feature. My question is
whether or not the xmlns-uris feature can be true while namespaces is false
or namespace-prefixes is true. Obviously this would make little sense but
nothing in the specs (that I could find) forbids it. Should it be forbidden?
If so what is the correct action? A SAXNotSupported exception? Or having the
side-affect of changing the associated features? I suppose that this
question applies similarly to the namespaces and namespace-prefixes
features.

Thanks,
Jeff Rafter