I can't see the problem in asking the purpose of the visit ------- no point though, no one is going to say - 'oh, I am off to chop off some heads'
I have no idea how we handle it - but what is for sure is any person who goes overseas to fight in 'any' war that Australia isn't involved in other than our own military personnel ------------ should NOT be allowed back in.
Now, I have no idea how we handle that if they are Australian born or only have an Aussie passport - but, we should make it happen.
If they have dual citizenship ---------- easy - cancel the Aussie citizenship.
If they don't? Well, Sarah Island comes to mind.
But, whatever we do - we do NOT want em back. - well, dead is probably ok, but, that's as far as compromise goes.