The dual citizenship debacle engulfing Australian politics will return to the High Court in Canberra for a hearing on October 10, 11 and 12 as the legitimacy of several parliamentarians remains uncertain.
Four senators and deputy prime minister Barnaby Joyce were referred to the court earlier this month after it was revealed they did not meet the sole citizenship requirement of section 44 of the constitution.
South Australian Senator Nick Xenophon and NSW Senator Fiona Nash will also be referred to the court over their British citizenship by descent when federal parliament next sits in September.
Senator Roberts remains the most at risk of being disqualified from parliament as he may have officially renounced his British citizenship after his nomination, the court heard.
Solicitor-General Stephen Donaghue QC said there was a "clear demarcation line" between the politicians - those who had known they were a citizen of a foreign power and those who did not.
Senator Roberts was born in India under British rule and applied to be an Australian citizen when he was 19-years-old.
Similarly, Western Australian Greens Senator Scott Ludlam was born in New Zealand and moved to Australia when he was three.
Mr Ludlam, who resigned on July 14, became an Australian citizen when 19 and like Senator Roberts will be tested as to whether he took reasonable steps to renounce his allegiance to a foreign power.
The politicians who did not know they were a citizen of a foreign country may escape disqualification because it was less reasonable for them to take steps to find out, the court heard.
In the case of Queensland Liberal Senator Matt Canavan, who was born on the Gold Coast to Queensland-born parents, he was unknowingly signed up for Italian citizen by his mother in 2007.
The court heard a retrospective change to Italy's laws made Senator Canavan's mother eligible for citizenship even though she had spent all her life in Australia.
Similarly for Mr Joyce, his father was born in NZ while it was under British law and inherited NZ citizenship retrospectively in 1949 after he moved to Australia.
That was then passed onto Mr Joyce without his knowledge.Former senator Larissa Waters, who resigned on July 18, was born in Canada to Australian parents a week before their laws changed to no longer require people to actively renounce their citizenship.
Senator Nash's father was born in Scotland, making her a British citizen, while Senator Xenophon is also entitled to British citizenship through his Cypriot father, who was born on the Greek Island while it was still a British colony.