Proposed resolution:

Add a sentence at the end of [locale.statics], paragraph 2: 

No library function other than locale::global() shall affect the value returned by locale().

It appears there's an important guarantee missing from clause 22. We're told that invoking locale::global(L) sets the C locale if L has a name. However, we're not told whether or not invoking setlocale(s) sets the global C++ locale.

The intent, I think, is that it should not, but I can't find any such words anywhere.