Who is caught up in Australia's dual citizen saga?

An Australian flag Image copyright Getty Images
Image caption Australian MPs are not allowed to be citizens of "a foreign power"

Seven Australian politicians will learn in October whether their elections to parliament were invalid because they hold dual citizenship.

A hotly debated part of the constitution, Section 44(i), says candidates for federal office cannot be "a subject or citizen of a foreign power".

The Australian government has argued that only politicians who "voluntarily obtained, or retained" their foreign citizenship should be disqualified.

That argument will be tested in the High Court of Australia from 10 October. All had submitted their personal defences by Friday.

So who are the seven politicians, and what will they argue?

Barnaby Joyce, deputy prime minister

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Image caption Barnaby Joyce said he was "shocked" to learn of his dual status

Dual citizenship: New Zealand (renounced in August)

How did he acquire it? Mr Joyce was born in Australia but his father is from New Zealand, which automatically awarded the politician citizenship.

"Neither I, nor my parents have ever had any reason to believe I may be a citizen of another country," Mr Joyce said in August.

What is his defence? Mr Joyce cannot be held to account for having only the "mere knowledge" of his father's birthplace, his legal submission argues.

Unlike the other six, who are senators, Mr Joyce sits in the lower House of Representatives - meaning his eligibility could imperil the government's one-seat majority.

More: NZ confirms Joyce is citizen

Fiona Nash, government senator

Image copyright Reuters
Image caption Fiona Nash is deputy leader of the Nationals, the junior Coalition partner

Dual citizenship: UK (renounced in August)

How did she acquire it? Australian-born Ms Nash became a UK citizen by descent through her Scottish-born father, to whom she was estranged for much of her life.

Her older sisters were born in England and have UK citizenship.

What is her defence? That like Mr Joyce she had no previous knowledge of her citizenship.

"Her parents had informed her that unlike in the case of her sisters, who were British citizens by birth, she could only become a British citizen upon making an application, which had not occurred," her submission says.

More: Nash caught up in citizen saga

Matt Canavan, government senator

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Image caption Matt Canavan, also from the Nationals, has temporarily stepped down from ministry

Dual citizenship: Italy (renounced in August)

How did he acquire it? Mr Canavan has Italian grandparents. In July, he said his mother had organised his citizenship - without his knowledge - when he was 25. But he later said his mother had not done this.

According to his submission, Mr Canavan gained his dual status through an Italian court decision on citizenship by descent in 1983.

What is his defence? Mr Canavan did not have "allegiance to a foreign power" because he had no knowledge of his status, and Italian citizenship law is vague, his legal documents say.

More: How Canavan learned of predicament

Malcolm Roberts, One Nation senator

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Image caption Malcolm Roberts had disputed he was elected as a dual citizen

Dual citizenship: UK (renounced in December)

How did he acquire it?: Mr Roberts was born in India to a Welsh father in 1955, making him a UK citizen. He was naturalised as an Australian in 1974.

UK authorities said he revoked his citizenship five months after he was elected in Australia's July 2016 election.

What is his defence? Mr Roberts claims he took "bona fide" steps to relinquish his citizenship, but it was not made official until 5 December.

In September, a court ruled Mr Roberts had sent a renunciation query to an incorrect email address.

Nick Xenophon, independent senator

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Image caption Nick Xenophon has described his UK citizenship as "useless"

Dual citizenship: UK (British Overseas Citizenship)

How did he acquire it? Mr Xenophon's father was born in Cyprus when it was a UK colony, and the politician inherited British Overseas Citizenship.

He has played down the "third-class citizenship" as not even allowing him to live in the UK, describing it as a "colonial peculiarity".

What is his defence? His submission disputes that such a "slender connection" could render him "a subject or citizen of a foreign power".

Larissa Waters, former Greens senator

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Image caption Larissa Waters says she made an "honest mistake"

Dual citizenship: Canada

How did she acquire it? Ms Waters was born in Canada but left as a baby with her Australian parents. She said she was oblivious to her Canadian status until July.

What is her defence? Unlike the previous five MPs, Ms Waters resigned over her dual citizenship.

Her submission maintains her resignation "properly complied" with the constitution, accusing those who had not quit of "ignorance or wilful blindness".

The government argues that Ms Waters, along with its three MPs and Mr Xenophon, should not be ruled ineligible. There is speculation Ms Waters could return.

More: History-making breastfeed senator quits

Scott Ludlam, former Greens senator

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Image caption Scott Ludlam was first to reveal dual citizenship, igniting the saga

Dual citizenship: New Zealand

How did he acquire it? Mr Ludlam was born in New Zealand but his family left the country when he was three.

He said he had always believed - wrongly - that his New Zealand citizenship had expired when he became an Australian citizen in his teens.

What is his defence? Like Ms Waters, Mr Ludlam resigned and maintains he was right to do so. He filed a joint submission with his colleague.

The government argues that Mr Ludlam voluntarily retained his citizenship, and, along with Mr Roberts, should be ruled ineligible.

More: NZ citizenship costs senator his job