Former Greens senator Larissa Waters could make an early return to parliament if the High Court agrees with arguments being put forward by the Commonwealth.
The government has filed its official submission on the seven federal politicians who have been referred to the court over their citizenship status.
It argues only One Nation's Malcolm Roberts and former Greens senator Scott Ludlam were wrongly elected, while the Nationals' Barnaby Joyce, Fiona Nash and Matt Canavan, crossbencher Nick Xenophon and Ms Waters should not be disqualified.
The submission, on behalf of Attorney-General George Brandis, contends that Senator Roberts and Mr Ludlam did not take all reasonable steps to renounce their respective British and New Zealand citizenship before being nominated.
Under section 44 of the constitution, "a subject or a citizen ... of a foreign power" cannot stand for parliament.
The Commonwealth believes that should apply only to those who have "voluntarily obtained or retained" their status.
That would preclude five of the politicians - minus Senator Roberts and Mr Ludlam - all of whom were not aware they were or ever had been a foreign citizen, the submission says.
Ms Waters resigned in July upon discovering she still had Canadian citizenship but could return if the High Court agrees with the Commonwealth and she is nominated to replace herself by the Queensland Greens.
Greens leader Richard Di Natale is keen for her to return.
"She's a wonderful MP, a wonderful human being and she's made a great contribution to the parliament," he told Sky News on Wednesday.
Senator Di Natale was not surprised by the government's arguments for why its MPs and senators should not be disqualified.
"The government has basically decided it doesn't want to play by the rules," he said.
"The government's view is there will be rules for everybody else and a separate set of rules for themselves."
The matters will go before the full bench of the High Court on October 10.
