Looking at the GIO help, and GMF wiki, did not provide me with an explanation of what ban/ning/ned means: and I think that a decision on what it does - logically - is the first step.
There seem to me to be two options - is it:
- A prohibition on a member from participating in the group, temporarily or permanently, with them - some time later - being either unbanned or removed from the group: i.e. they remain a member of the group, but with 'banned' status (so they can't do anything)
- A 'removal with attitude': i.e. they are deleted from the group, with a 'banned = prevent from rejoining' flag set in their 'past member' record. (Should there be any other difference between a 'banned' and a 'removed' member?)
(The 'banned = prevent from rejoining' flag should also be set/carried into their 'past member' record in (1) if they are subsequently removed).