I have actually done quite a bit of research on this issue for a law school paper. Ideas cannot be copyrighted. The general problems with directors gaining copyright protection is that 1) most (not us theatre aficionados, but def. courts) see the work as originating with the playwright, and not the director, thus to most, the director does not create anything "original." But most importantly, in order to be copyrighted, something has to be fixed in a tangible form...while some have attempted to do so via prompt books and video, these raise a whole new set of copyright issues. At this point, I think the balance of copyright seems to favor allowing others to "borrow" some, as opposed to allowing copyrights for direction and perhaps creating an expensive licensing scheme, or just closing access to new director. The general (not well founded) argument against copyright protection is, "what, will someone own the right to enter stage right?". By the way, sorry for any grammatical errors, on my way to the gym. Hopefully, now that this issue is hot, my paper will be published, sans errors. :)
"Observe how bravely I conceal this dreadful dreadful shame I feel."