And this is why you get people to ruthlessly vet your preselected candidates. Suspect it would have been caught these days, but back in 2006 things in the Greens were a fair bit more lackadaisical.
He had no choice but to resign, but yeah, this sucks. He was the best parliamentary Green by a fair way in my opinion, walked the line between someone like Rhiannon who is all principled outrage and not enough brain, and Di Natale who is the reverse. With any luck he sorts the citizenship thing out and makes a return in some way.