Top Australian court will rule on lawmakers' dual citizenship

Australia's High Court began a three-day hearing on Tuesday to determine the eligibility of seven lawmakers who may hold dual citizenship, in a case that could determine whether the government is able to maintain its razor-thin majority.

Prime Minister Malcolm Turnbull's centre-right government holds just a one-seat majority in parliament, meaning its future could rest on the outcome of the citizenship crisis.

Australia's parliament was rocked by revelations in August that seven politicians, including the deputy prime minister and two other Cabinet members in Turnbull's coalition government, are dual citizens.

That means they are potentially ineligible to hold elected office in Australia under the constitution.

What are the arguments in court? 

The seven lawmakers accept they were dual nationals at the time of their election last year. 

But the government argues that five of them, including all three Cabinet members, should be cleared of any wrongdoing because they were unaware that they had contravened a constitutional requirement at the time.

The government argues that only two politicians who  "voluntarily obtained, or retained" dual status should be disqualified.   

Australian Solicitor-General Stephen Donaghue urged the seven justices of the High Court not to interpret the constitution literally.

Donaghue said instead the constitution should only disqualify politicians if they had prior knowledge that they may be dual citizens but did not take "reasonable steps" to investigate and renounce their second citizenship where needed.

A ruling could come as soon as Thursday.

The seven politicians under scrutiny include Deputy Prime Minister Barnaby Joyce.

Joyce acquired dual citizenship from his New Zealand-born father. He said in a submission to the court he believed that his father had renounced his New Zealand citizenship before he was born.

He did not know until he was 10 that his father was still a New Zealand citizen, Joyce said.

How will the outcome of the ruling affect Australia? 

Should the High Court rule that Joyce—the sole lower house lawmaker caught up in the crisis—is ineligible for office, Turnbull will then need to win the support of one of three independent lawmakers to keep his minority government.

Turnbull's government is already in a minority in the upper house Senate. Should the High Court disqualify all seven lawmakers, he will face a government reshuffle after losing two more Cabinet members who are senators.

Support for Turnbull continues to languish near a six-month low, but political analysts believe he might receive a boost if he is able to win passage of a same-sex marriage bill.

Turnbull's government won High Court approval last month to stage a non-binding postal survey on the issue, which is widely popular among Australians.

Results of that poll will be announced on November 15.