A total of seven federal politicians, including Deputy Prime Minister Barnaby Joyce, will learn on Friday if they are eligible to sit in parliament.
The landmark High Court decision will be handed down from 2:15pm AEDT and threatens the government's one-seat majority should Mr Joyce be ruled ineligible.
Prime Minister Malcolm Turnbull will also learn whether a by-election will need to be held in Mr Joyce's northern NSW seat of New England.
So, what happens after the judgments on the eligibility of Mr Joyce, Nationals Senator Matt Canavan, Deputy Nationals leader Fiona Nash, South Australian Senator Nick Xenophon, former Greens Senators Larissa Waters and Scott Ludlam, and One Nation Senator Malcolm Roberts?
Related reading
High Court will rule on Citizenship Seven case on Friday
Barnaby Joyce
If he wins, he remains in parliament. If disqualified, Joyce will be forced to a by-election in his NSW seat of New England. He is likely to retain the seat. But the government, which has a majority of just one seat, will have six weeks of anxiety and distraction. Independent Tony Windsor could put up a solid fight if he decides to run again. A by-election loss would deliver minority government. Labor has advice his post-election ministerial decisions are open to legal challenge.
Fiona Nash
If she wins, she'll remain in parliament. If she loses, Senator Nash's Senate seat would ordinarily go to the next person on the NSW coalition ticket, who is this case is the Liberal Hollie Hughes. But the Nationals may insist on one of their own taking it, which would likely require Hughes to take up the seat, resign and cause a casual vacancy. Hughes is disqualified from sitting at the moment because she holds a government job at the Administrative Appeals Tribunal.
Matt Canavan
If he wins he will remain in parliament and is expected to get his cabinet post back. If he loses, the next candidate on the Queensland Liberal-National Party ticket was Liberal Joanna Lindgren. But she would be required to sit in the Nationals party room.
Malcolm Roberts
If he wins the case he will remain in parliament. If he is disqualified his seat will go to the next candidate on the Queensland One Nation ticket, Fraser Anning. Anning was facing bankruptcy proceedings which would have ruled him out of the seat, but the case has been dropped.
Nick Xenophon
Senator Xenophon will be quitting parliament whatever the court rules. If he is disqualified the next person on the NXT ticket is business consultant Tim Storer. If he wins the case, there will be a casual vacancy to be filled by NXT. At least three other senior NXT members are interested.
Larissa Waters
Ms Waters has already resigned from the Senate. If disqualified she will be replaced by the next person on the Queensland Greens ticket, former Democrats senator Andrew Bartlett. If she wins the case there will be a casual vacancy which the Greens will fill. Having renounced her Canadian ties, the former environmental lawyer could be restored to the seat.
Scott Ludlam
Mr Ludlam has also resigned. The next candidate on the West Australian Greens ticket is 23-year-old student Jordon Steele-John. Even if he is cleared, Ludlam says he has no interest in politics in the short or medium term.
What has happened so far?
Section 44 of the Constitution prevents dual citizens from being a member of parliament.
During the High Court hearings, government lawyers argued five of them should be ruled eligible, except for Mr Ludlam and Senator Roberts, because they did not know they were dual citizens.
Solicitor-General Stephen Donaghue argued it was reasonable that where a person had no knowledge they ever were a foreign citizen, they should not need to take any steps to renounce their citizenship.
The government told the court 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.
Mr Turnbull is travelling to Israel for a five-day trip on Friday for the Battle of Beersheba commemorations, raising questions as to who will be acting prime minister should Mr Joyce and Senator Nash be ruled ineligible.
There have been reports Deputy Liberal leader and Foreign Minister Julie Bishop would assume that role should there be adverse findings against the cabinet ministers.
Meanwhile, Labor has received legal advice any decisions made by Mr Joyce, and Senators Nash and Canavan are open to a court challenge.
Section 64 of the constitution says 'no minister of state shall hold office for a longer period than three months unless he or she becomes a senator or member of the House of Representatives'.
Labor's advice is this would apply from the swearing-in date of a minister.
'Any decision made by the person in his or her purported capacity as a minister after three months has lapsed after his or her appointment as a minister is open to challenge,' the advice from Matthew Collins and Matthew Albert says.
The government has dismissed any concerns.
Ms Waters and Mr Ludlam have already resigned from parliament over their dual citizenship by birth in Canada and New Zealand respectively.
India-born One Nation Senator Roberts was found by the High Court in September not to have properly renounced his UK citizenship by descent - through his Welsh father - at the time of his 2016 election nomination.
Mr Joyce and Senators Canavan, Nash and Xenophon were born in Australia but were made citizens by descent.
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 next year.
Share
