The Greens are an international movement that has established political parties in most Western democracies. They're consistently anti-war, with an idealistic belief in non-violent methods of conflict resolution. Their policy platform is consistent worldwide.
Just like the UK, Australia has passed legislation to make it illegal for citizens to join Islamic State. The British Greens leader, Natalie Bennett, believes that it should not be a crime to join it. Never mind that there is a very real risk that Western citizens may return from fighting with Islamic State, and then carry out terrorist attacks in their home countries. The very real security risk these people pose makes this legislation necessary.
Perhaps Bennett and her fellow Greens envisage sitting down with these terrorists over stuffed vine leaves, hummus, and hookah, civilly talking through their grievances. Never mind that they're dealing with zealots who are not the least bit interested in negotiating. To them, the West is an enemy. They are infidels. They offer them three choices. Convert to their form of Islam, accept dhimmitude, or death.
Bennett made her statement on the very same day that another media report appeared about the genocide that Islamic State is carrying against Christians in its conquered territories.