CANBERRA, Australia (AP) — Australia's High Court will rule Friday on whether seven lawmakers including the deputy prime minister and two senior ministers are eligible to sit in Parliament in a case that threatens the conservative government's slender majority.

Prime Minister Malcolm Turnbull has said he is confident that the seven judges will not take a literal interpretation of a 116-year-old section of the constitution that bans "a subject or citizen of a foreign power" from sitting in Parliament.

The fate of Deputy Prime Minister Barnaby Joyce is most crucial to the government in an unprecedented political crisis.

If the court rules that he was illegally elected in July last year due to New Zealand citizenship he unknowingly inherited from his father, the ruling coalition could lose its single-seat majority in the House of Representatives, where governments are formed.

Joyce could stand in a by-election, having renounced his Kiwi citizenship. But the government is unpopular in opinion polls, and the rural voters he represents could throw both Joyce and his administration out of office. The earliest possible date for such an election is Dec. 2.

Six senators could be disqualified, though the balance of power would not change since senators can be replaced without elections. Two of them however are government ministers, Fiona Nash who inherited British citizenship from her father and Matt Canavan who became an Italian through his maternal grandparents.

Contentious decisions made by ineligible ministers could be challenged in the courts.

At the emergency hearing two weeks ago, the High Court heard doubts about whether Canavan's Italian citizenship was valid.

The Australian Constitution took effect in 1901 and only two lawmakers before now had ever been caught by the ban on dual nationals.

In both cases, the lawmaker was born overseas and was disqualified from Parliament. But four of the seven currently under a cloud — the three ministers and Nick Xenophon, leader of a minor party — are Australian-born and did nothing to become foreign citizens.

The government argued that only New Zealand-born Scott Ludlam and India-born Malcolm Roberts should be disqualified. The government argues that those two senators from minor parties failed to take reasonable steps to ensure they were not dual nationals.

Government lawyer Stephen Donaghue told the High Court judges the other five lawmakers should not be disqualified because they did not voluntarily acquire or retain citizenship of another country.

"If a person is not aware either that they are a dual citizen or of a significant prospect that they are, in our submission by definition that person cannot have a split allegiance," Donaghue told the court.

Bret Walker, a lawyer for Joyce and Nash, told the court that neither knew until recently that they were dual citizens of New Zealand and Britain, respectively.

As soon as they found out, they took all reasonable steps required to sever their foreign ties, Walker said.

"There's no split allegiance where you're not aware of one," Walker told the court. "You cannot heed a call you cannot hear."

Roberts, who became a British citizen through his Welsh father and represents the anti-immigration, anti-Muslim One Nation party, argued through his lawyer Robert Newlinds that it would be "Un-Australian" to treat Australian-born citizens differently to immigrants.

Public attention has focused on lawmakers' eligibility since July 14, when Ludlam, the then-deputy leader of the minor Greens party, revealed he was still a Kiwi and had been unlawfully elected to the Australian Senate three times since 2007.

Days later, Larissa Waters, the Greens co-deputy leader, revealed that she retained the citizenship of Canada, where she was born. She and Ludlam are the only lawmakers among the seven who have accepted that they are not eligible to sit in Parliament and have quit.

Many question whether the ban on dual citizen lawmakers is appropriate in a nation of immigrants where around half the population was either born overseas or has a migrant parent.