Seven members of the federal parliament will have their eligibility tested by the High Court in a three-day hearing starting on Tuesday.
Australia's constitution bans anyone holding dual citizenship from sitting in parliament, in a section aimed at ensuring MPs do not hold split allegiances.
The government will argue the phrase "is a subject or citizen ... of a foreign power" should be seen to refer only to a person who has voluntarily obtained, or retained, that status.
As well, the Solicitor-General Stephen Donaghue will argue it is reasonable that where a person has no knowledge they ever were a foreign citizen, they should not need to take any steps to renounce their citizenship.
Greens senators Larissa Waters and Scott Ludlam have already resigned from parliament over their dual citizenship by birth in Canada and New Zealand, respectively.
India-born One Nation senator Malcolm Roberts is also likely to fall after being found by the High Court in September of not having properly renounced his UK citizenship by descent -through his Welsh father - at the time of his 2016 election nomination.
The government will argue Deputy Prime Minister Barnaby Joyce, former minister Matt Canavan, deputy Nationals leader Fiona Nash and crossbench senator Nick Xenophon will "stand or fall together", given their similar circumstances.
All four were born in Australia but have given sworn evidence they had no knowledge the law of another country had made them citizens by descent.
The case of Mr Joyce will be most closely watched because if he is disqualified the government, which holds a one-seat majority, will face a by-election in his NSW seat of New England.
Prime Minister Malcolm Turnbull is confident, based on the solicitor-general's advice, that Mr Joyce, Senator Nash and Senator Canavan will be cleared.
Senator Xenophon, who found himself to have British citizenship by descent, will leave parliament whatever happens to contest the South Australian state election in March 2018.