One of Australia's new senators, One Nation's Malcolm Roberts, sent a bizarre affidavit to then prime minister Julia Gillard in 2011 demanding to be exempt from the carbon tax and using language consistent with the "sovereign citizen" movement.

Mr Roberts has also written numerous reports claiming climate change is an international conspiracy fostered by the United Nations and international banks to impose a socialist world order. At least one report cites several anti-Semitic conspiracy theorists, including notorious Holocaust denier Eustace Mullins among its "primary references".

Anti-government, self-identified "sovereign citizens" claim to exist outside the country's legal and taxation systems and frequently believe the government uses grammar to enslave its citizens.

NSW Police say such people "should be considered a potential terrorist threat".