At illegality.
Well, haven't you wrapped yourself up in a nice blanket?
If the law allows it, then it is legal...
Sure, blanket, whatever. I'm not speaking in general terms, here. I'm speaking of this case. There has been a massive influx of foreign fighters to IS, dozens of whom are confirmed Aussies. Australian intelligence determined that illegality was imminent, and acted to thwart it. In this instance, I'm willing to give law enforcement the benefit of the doubt.