Do they have to block service in Australia
If it's a free service I would think just have a check box "Are you in Australia [ ]" If you check it, OK, Bye.
If you lie and say you don't live in Australia, well not my fault.
This reminds be of the days of 40 bit international versions of browsers with the download page for the better US version where you swear not to give it to China or other "bad" countries. That worked great.