I guess that would depend on the club's preference, with a bit of coding I could offer:
1) readable by all, and open to post to all
2) readable by all, but posting only possible by club/organisation members
3) readable only by club/organisation members, posting only possible by club/organisation members
That would cover all eventualities, and wouldn't require much additional work to integrate.
my orders are to sit here and watch the world go by