Fine Gael Senator, Mr Jim Higgins and Labour TD Brendan Howlin have been given leave by the High Court to challenge a decision by the Morris Tribunal ordering them to name their informant in relation to allegations of garda corruption in Co Donegal.
Mr Justice O'Neill gave both men leave to apply, by way of judicial review, for an order quashing a decision of the Tribunal chairman, Mr Justice Morris, directing them to produce the information in their possession, including their telephone records.
The two politicians both received information relating to allegations against gardai in Donegal, and brought it to the attention of the then Minister for Justice, Mr John O'Donoghue.
Both were TDs at the time, though Mr Higgins lost his seat in the last election.
The allegations concerned two senior members of the Garda Siochana, and centred on the claim that one of the gardai under investigation had worked closely with two high-ranking members of the force, and as a result that the allegations against him were not being pursued vigorously.
The claims came in a number of phone calls and documents received by the two politicians. These are the subject of a separate module of the Morris Tribunal.
The tribunal has asked Mr Higgins and Mr Howlin to identify the source of these allegations, but they have refused, citing privilege under Article 15.10, 15.12 and 15.13 of the Constitution, which all relate to Dail privilege.