Territory Rig is the style of dress which men adopt in the Northern Territory on official occasions, comprising long trousers, shirt and tie. Territory Rig may incorporate thongs as footwear but they must be high quality 'double pluggers'.
Territory Rig is also sometimes called Darwin Rig.
The expression has expanded to be used as a formal dress code for both men and women. The Northern Territory Government officially defines Territory Rig for Gentlemen as trousers, long sleeved-shirt and tie, and for Ladies as day dress/after five
References
Territory Rig Wikipedia(Text) CC BY-SA