[jujucharms.com:jamesbeedy@external/prm-demo] ubuntu@ip-10-20-100-90:~ 
$ juju models
Controller: jujucharms.com

Model                  Cloud/Region   Status     Access  Last connection
common-infrastructure  aws/us-east-1  available          never connected
feed-demo              aws/us-east-1  available          never connected
feed-staging           aws/us-east-1  available          never connected
jujucharms-test        aws/us-east-1  available          never connected
prm-demo*              aws/us-east-1  available          never connected
prm-staging            aws/us-east-1  available          never connected

[jujucharms.com:jamesbeedy@external/prm-demo] ubuntu@ip-10-20-100-90:~ 
$ juju grant simonbacquie admin prm-demo
ERROR unsupported domain ""