Labor's Katy Gallagher's future to become clear

Labor Senator, Katy Gallagher, will learn her fate on Wednesday, when the High Court rules if she's a dual national, and ineligible to sit in Parliament.

The decision could have much wider implications, with a number of Labor MPs under the same citizenship cloud.

If the High Court decides she shouldn't be in the Senate, the Turnbull Government, could, theoretically, refer others, potentially leading to a series of by-elections.

The ACT senator argued she took all reasonable steps to renounce her British citizenship.

The Solicitor-General told the court in March that it was clear Senator Gallagher had not complied with the requirements.

The government has argued Labor members Justine Keay, Josh Wilson, and Susan Lamb should resign if the High Court rules against Ms Gallagher.

There was talk they would be referred, but there's growing doubt the government wants a number of costly by-elections.

The dual citizenship sage has already claimed a long list of victims, including then-deputy Prime Minister, Barnaby Joyce, who was returned to Parliament in an ensuing by-election.

Others to fall include the Greens' Larissa Waters and Scott Ludlam, One Nation's Malcolm Roberts, Labor's David Feeney, and Independent Jacqui Lambie.

The High Court decision is due to be handed down at 10.15am.