The former Army commandant, Edward Horgan, has lost his constitutional challenge to the legality of the Government allowing American troop carriers to land at Shannon Airport.
He had claimed it amounted to a participation in war and was contrary to Ireland's constitutional commitment to seeking peaceful settlements to conflicts.
The court ruled it could not interfere in the decisions made by the Oireachtas and could not second guess the Government on such issues.
A decision on costs will be made on Friday.
Harney heckled by anti-war protestors
The Tánaiste, Mary Harney, was heckled by four anti-war protestors who disrupted a tree-planting ceremony in Shannon this afternoon.
Ms Harney was visiting Shannon Town Centre to formally launch details of a €135 million re-development of the town centre.
During a tour of the centre, a number of protestors shouted anti-war slogans and raised a number of anti-war banners.
They also shouted 'shame' while Ms Harney was delivering her speech.
The Tánaiste defended the Government's decision to allow Shannon to be used by the US military during the war in Iraq.
In relation to the re-development of Shannon town centre, the promotors said that they were prepared to lead a consortium of business interests in the region to develop a new rail link between Shannon, Limerick and Ennis.
The Tánaiste said she would support such a a rail link, but would make no promises about committing Government funds to any proposed project.