Ah, Ok, I see where we are having a problem understanding each other.

Under the vBulletin software I can set a forum section to open or closed. There is no other option.
If it is open anyone may post in that section. It would take a Moderator to close a thread.

If the forum is closed no one may post to it. A Moderator could move a thread into a closed section thereby stopping follow-on posts but not even a Moderator can post to a closed forum section

So while a good idea I do not know of a way we could actually make it work given the limitations of the software.