A High Court challenge to the use of Shannon airport by Iraq-bound US military aircraft will open this morning.
The action is being taken by retired army Commandant, Edward horgan, from Castletroy in County Limerick.
It is expected to last until the end of the present law term on 11 April and judgement is likely to be reserved.
Edward horgan is challenging the state's granting of landing rights at Shannon airport to US planes bound for Iraq.
His Senior Counsel, John Rogers, has said his case is that a neutral state has a duty under international law not to permit the movement of troops and munitions on its territory.
He will call a military witness who will testify that allowing over-flights and refuelling at Shannon by the US military constitutes participation by Ireland in war.
Mr horgan's case will rely on Article 29.3 of the Constitution.
The case will be heard by Mr Justice Nicholas Kearns.
The State and Government will be represented in the challenge and are expected to mount a strong defence.
Whatever the outcome, the case is likely to go on appeal to the Supreme Court.
It has already been indicated that a judgement in the High Court action is unlikely before the end of April.
An appeal to the Supreme Court would mean a final decision is unlikely for at least another month after that.