The High Court has granted Sinn Féin's Senator Pearse Doherty leave for a judicial review into why the Donegal South-West bye-election has not yet been held.
Mr Justice Peart granted the application after a brief hearing.
The Government has until 29 July to return a defence at which stage a date for the full hearing of the case will be sought.
The Donegal South-West seat has been vacant since the election of Fianna Fáil's Pat 'the Cope' Gallagher to the European Parliament in June last year.
There are two other vacancies in the Dáil at present.
They are the seats vacated by George Lee of Dublin South in February and by Martin Cullen of Waterford in March.