Comment 3 for bug 817872

John,
   This is the closest I could find: http://docs.amazonwebservices.com/AWSEC2/latest/CommandLineReference/ApiReference-cmd-ModifyInstanceAttribute.html. But notice that you change the security group but cannot remove a security group from an instance. The only thing you can do is terminate all the instances and then delete the security group. I think we should still put in the check for instances upon deletion and raise an exception.