[e-Newsletter] Disable unsubscibe for particular membergroup

Hi,
We let users (un)subscibe for certain member-groups. But there is 1 member-group where we don't want the user to be able to unsubscribe. They always have to be subscribed to that group so they will receive all emails being sent to that group.
We allready removed the unsubscribe link in the newsletters which we mail to that group. But when a registered user is visiting his dashboard he can select "Unsubscribe all" or just uncheck the checkbox for that group.
How can we make sure they cannot unsubscribe for that group?
When searching the forum I noticed more people would appreciate such an option. Perhaps it's an idea for the developers to add a Yes or No radio-button with the text "May user unsubscribe this group?" when the admin is making a new member-group.

With kind regards,
Age