The European Commission is challenging the Government over Ireland's decision to bypass the European Court of Justice (ECJ) in its campaign to close the Sellafield nuclear plant.
The commission will argue at a hearing in Luxembourg on Tuesday that Ireland has breached the exclusive jurisdiction of the ECJ by taking a legal case against Britain to the UN Convention on the Law of the Sea (UNCLOS) on the Sellafield issue.
The legal action represents the latest twist in a four-year campaign by the Government to try to force Britain to close the Sellafield nuclear power plant, which the Irish authorities allege is a risk to the environment and human health.
A victory for the commission would be a major setback for the Government, which may have to drop its case and institute new legal proceedings at the ECJ - a situation that would further delay Ireland's legal campaign against Sellafield.
If the Government prevails in the case, UNCLOS would be able to proceed with its deliberations in the original case.
In 2001 Ireland instituted proceedings before UNCLOS stemming from Britain's failure to provide the Irish authorities with a copy of an assessment, conducted by a private consultancy firm, of the economic justification for the Mox facility at Sellafield. In its case the Government also cited ongoing environmental and health concerns regarding emissions from the Sellafield plant.
The UN tribunal subsequently demanded several interim measures, including further exchanges of information between Britain and Ireland, the monitoring of potential risks for the Irish Sea, and pollution prevention measures.
However, the proceedings through the UNCLOS court are adjourned due to the current legal action taken by the commission against the Government, delaying a final ruling in the case.
The commission is arguing that environmental protection constitutes an area of shared competence in EU law, and that community institutions should be given precedence as the forum for dispute resolution rather than the UN.
The legal action being taken by the commission is procedural and would not result in any fines on Ireland if the State were to lose.
However, a finding against the Government could result in a lengthy delay to its legal campaign against Sellafield and the British government.
A spokesman for the Minister for the Environment said yesterday it would dispute the commission's case and would continue to work towards shutting Sellafield.
"The Irish Government's position on Sellafield is clear: we want a cessation of the activities at Sellafield and ultimately the closure," he added.