The High Court could decide the fates of seven politicians embroiled in a dual citizenship saga as early as Thursday.
The full bench, sitting as the Court of Disputed Returns, is preparing for the third and final day of a hearing into the eligibility of the federal MPs.
Each are facing questions over their citizenship, with the constitution banning dual nationals from sitting in parliament to guard against split allegiances.
Lawyers for One Nation's Malcolm Roberts will plead their case when the hearing resumes in Canberra.
There is no indication yet on when a judgment might be released, but Attorney-General George Brandis says High Court judges are aware of the public importance of making a decision within a reasonable time frame.
"Ordinarily it's a matter of weeks or a couple of months, but of course their honours would be well aware of the public importance of knowing the outcome of these proceedings as soon as they may reasonably be known," Senator Brandis said on Wednesday.
Barnaby Joyce and his Nationals colleagues Fiona Nash and Matt Canavan have all argued they should be spared the court's wrath. So too has crossbench senator Nick Xenophon.
But the lawyer for former Greens senators Scott Ludlam and Larissa Waters says the pair were right to resign, and argued the other five ought follow suit.