The Ban Member
feature should be used with care. Banning removes the member and prevents the
member from rejoining the group until the ban is removed.
To ban a member:
Note: You can also ban the author of a message directly from the individual message page by clicking Ban author under their Yahoo! ID.
To later remove the ban:
Note: You can ban a person from your group even if that person is not already a member. This allows you to prevent people you know to be troublesome from joining your group in the first place.