When is a punishment not a punishment?
Is visa cancellation a punishment? Most people would think so. It can have pretty devastating effects. For one thing you can be arrested (sorry, "detained") and locked up in a jail (sorry, "detention centre"). Then you can be deported (sorry, "removed").

The official view is that all of this is "administrative", not "punitive". An interesting view from the other side can be found in an article in the Sydney Morning Herald by Royal Abbott.