Ability to Remove Event Organiser Permissions
Currently if you make someone an event organiser or if they organise an event as an assistant organiser they gain the ability to email the group forever.
The only way you can remove this permission is by kicking them out of the group. This is not ideal. It should be possible to control this.
If a member no longer has the role of Event Organizer or Assistant Organizer, they will lose the ability to email the group in the way you describe.
If this is giving you trouble, please write in to email@example.com with more details.
Duncan Malcolm commented
Awesome, thanks :-)
@Matt: That may work going-forward, thank you. What about still current members?
One way to handle this is to make the person an Event Host (essentially a one-time Event Organizer). After the event passes, their privileges go back to a member and they will no longer have the ability to email the entire group.