Rollback
For the Group Remove method, rollback consists of calling the
Group Add method. Prior to removing the object from the group, the
provider stores both the group path and the object path so that the
object can be re-added to the group in case rollback is
required.
Note
Prior to this action, the provider should ensure that the object
specified is a member of the specified group. This ensures that
rollback of a group remove operation does not actually add an
object to a group of which it was not previously a member.