Blocking is done by members.
You would not be the first to receive a message and then be blocked from replying.
Blocked by the person! You can't send messeges to the person if he has blocked you
You will get the same thing if you receive a message from a member that has their privacy settings to friends only.
I know if they're an admin in a club,they can create announcements that send messages, regardless of their privacy settings. I actually haven't tested that setting to see if only sending to friends happens for regular messages or not